IMac freezes plus pixelated screen when restarted.

My iMac has been freezing and when I restart it the screen goes into black & white pixels after the grey start-up and blue screens. If I soft boot and hold down the D key when starting it works okay. Any ideas? I have an iMac 2.46HZ Intel Core 2 Duo 4GB 667 MHz DRR2 SDRAM. Please keep any help as simple as possible since I'm not very tech savy. Thanks!

I think it's a GPU issue. GPU problems appear and disappear, so I'm not surprised that your iMac sometimes works correctly.
I recommend you to take the iMac to an Apple Store or reseller. The GPU is soldered onto the logic board, so this may be an expensive repair

Similar Messages

  • Why does my imac get a black screen when switching on

    why does my imac get a black screen when turning on, and logging in is very slow.

    I would first reset the SMC:
    Shut down and unplug the Mac.
    Keep the Mac unplugged for at least fifteen seconds.
    Plug the Mac back in and do not turn it back on for at least five seconds.
    Press the power button to turn the Mac back on.
    Then I would reset the PRAM by rebooting the iMac while simultaneously holding the Command-Option-P-R keys until the machine restarts a second time.
    Let us know if these  procedures don't solve the problems.
    Hope this helps

  • IMac Freezes Periodically During Screen Saver Only

    I own a late-2006 Intel-based iMac. Over the last few months, I've noticed that the iMac freezes when the screen saver is running. This doesn't happen all the time, and it doesn't matter what screen saver I use. (None of the screen savers is a third-party.) The iMac doesn't freeze at any other time.
    Any ideas?
    - Keith
    P.S. I'm running Snow Leopard right now, and it happens even with Snow Leopard, just as it did with plain ol' Leopard.

    Your iMac has a dedicated Graphic's chip (GPU), while some of the Late 2006 17" iMacs had a GMA 950 graphics processor with 64MB of DDR2 SDRAM that shared with the main memory. To check which Graphic's chip you have go to: Apple > About This Mac > More Info and in the Hardware section select Graphics/Display.
    If you would like to monitor the temperature of your GPU, CPU, HD and Memory check out the iStat Pro widget > http://www.islayer.com/apps/istatpro/
    The main reason I suspect the lack of RAM over an overheating GPU is because you only reported a problem with the Screen Saver and not with other intense graphic's like movies, videos or games.
    Please let us know how you make out with the RAM upgrade.
    Dennis

  • First version MacBook Pro, 10.6.8, freezes with pixelated screen. Repaired HD with Disk Utility, but still happens.  Temp gague shows max of 51C. Any ideas?

    I have the first version MacBook Pro, running 10.6.8 (most current OS that works).  It freezes with a pixelated screen. This may not happen for weeks, or it may happen every time i restart.  I repaired the hard drive with Disk Utility, but the problem still happens.  The temp gague shows a max of 51C. Any ideas on what could be causing this?

    I have the first version MacBook Pro, running 10.6.8 (most current OS that works).  It freezes with a pixelated screen. This may not happen for weeks, or it may happen every time i restart.  I repaired the hard drive with Disk Utility, but the problem still happens.  The temp gague shows a max of 51C. Any ideas on what could be causing this?

  • IMac stuck at gray screen when booting

    Hi - My 2011 iMac with 10.8.2 is stuck on the gray screen when rebooting. I was in Windows 7 bootcamp, and restarted to OS X. I see the screen below, and once the progress bar reaches 100%, the computer shuts off. Every time I reboot, the same problem. I've disconnected everything, except for the standard bluetooth wireless keyboard. I've tried some various boot options, such as holding down Shift while rebooting, as well as command+R, but neither had any impact, it is the same problem over and over. Any tips on what to try next?

    If you want to preserve the data on the internal drive(s), you must try to back up now, before you do anything else. It may or may not be possible. If you don't care about the data, you can skip this step.
    There are several ways to back up a Mac that is unable to fully boot. You need an external hard drive to hold the backup data.
    1. Boot into Recovery (command-R at startup) or from a local Time Machine backup volume (option key at startup.) Launch Disk Utility and follow the instructions in the support article linked below, under “Instructions for backing up to an external hard disk via Disk Utility.”
    How to back up and restore your files
    2. If you have access to a working Mac, and both it and the non-working Mac have FireWire or Thunderbolt ports, boot the non-working Mac in target disk mode by holding down the key combination command-T at the startup chime. Connect the two Macs with a FireWire or Thunderbolt cable. The internal drive of the machine running in target mode will mount as an external drive on the other machine. Copy the data to another drive. This technique won't work with USB, Ethernet, Wi-Fi, or Bluetooth.
    How to use and troubleshoot FireWire target disk mode
    3. If the internal drive of the non-working Mac is user-replaceable, remove it and mount it in an external enclosure or drive dock. Use another Mac to copy the data.

  • IMac Flat Panel Gray Screen when I Turn On

    My iMac won't load. When I turn it on there is the "chime" then nothing but a gray screen. I tried reseting the PMU, but still nothing. The machine froze while doing a backup and my hubby forced the machine off. When I tried to turn on the next day, this is what I got. Have tried starting it with everything unplugged... I am in the USVI and there are no Apple people here so I really need some HELP!

    Since the problem seems to have started with the forced shutdown, try repairing the hard drive following the steps in Trav's Tips
    You can also review this Apple KB Article
    Try repairing the disk first and see if that does the trick.
    Good luck (although since you're in the VI's your luck seems to be pretty good!)
    Clint

  • IMac freezes at login screen for file server

    The machine: iMac (lampshade), OS 10.3.9
    The symptom: During the boot/login sequence, the machine locks up at the login screen to the file server.
    If I disconnect the network cable during the boot sequence, it will error but not freeze; I can later reconnect the cable and login without a problem.
    Any ideas?
    James

    You may want to look at this similar post:
    http://discussions.apple.com/thread.jspa?messageID=690609&#690609
    Heres what Mac Help said.
    Open System Preferences and click Startup Disk.
    If necessary, click the lock icon and type the name and password for an administrator user.
    Click the icon of the system folder or system volume that you want to use, then click Restart.
    IMPORTANT: When selecting a network startup volume, be sure you select a valid network startup volume and not a network install image. Choosing a network install image reinstalls your system software and may erase the contents of your hard disk. A standard network volume icon appears as a globe and Mac OS X system folder. When you select a network volume icon, a message appears in the Startup pane describing the volume. A network install icon appears as a globe with downward pointing green arrow.
    Another way to select a startup disk is to hold down the Option key as you restart your computer. You'll see the available startup disks and can select one.
    If your computer is on a network and a network startup volume is available, you can start up from the network startup volume by holding down the N key as you restart your computer.

  • Imac freezes with gray screen after mavericks update

    I was updating my imac system and it is frozen in a gray screen, like it is restarting.
    It's been twenty minutes and it didn't restarted.
    What can i do if it don't restart anymore?
    All my work data is on that imac.

    Take each of these steps that you haven't already tried. Stop when the problem is resolved.
    Step 1
    The first step in dealing with a startup failure is to secure the data. If you want to preserve the contents of the startup drive, and you don't already have at least one current backup, you must try to back up now, before you do anything else. It may or may not be possible. If you don't care about the data that has changed since the last backup, you can skip this step.   
    There are several ways to back up a Mac that is unable to start. You need an external hard drive to hold the backup data.
         a. Start up from the Recovery partition, or from a local Time Machine backup volume (option key at startup.) When the OS X Utilities screen appears, launch Disk Utility and follow the instructions in this support article, under “Instructions for backing up to an external hard disk via Disk Utility.” The article refers to starting up from a DVD, but the procedure in Recovery mode is the same. You don't need a DVD if you're running OS X 10.7 or later.
    b. If Step 1a fails because of disk errors, and no other Mac is available, then you may be able to salvage some of your files by copying them in the Finder. If you already have an external drive with OS X installed, start up from it. Otherwise, if you have Internet access, follow the instructions on this page to prepare the external drive and install OS X on it. You'll use the Recovery installer, rather than downloading it from the App Store.
    c. If you have access to a working Mac, and both it and the non-working Mac have FireWire or Thunderbolt ports, start the non-working Mac in target disk mode. Use the working Mac to copy the data to another drive. This technique won't work with USB, Ethernet, Wi-Fi, or Bluetooth.
    d. If the internal drive of the non-working Mac is user-replaceable, remove it and mount it in an external enclosure or drive dock. Use another Mac to copy the data.
    Step 2
    If the startup process stops at a blank gray screen with no Apple logo or spinning "daisy wheel," then the startup volume may be full. If you had previously seen warnings of low disk space, this is almost certainly the case. You might be able to start up in safe mode even though you can't start up normally. Otherwise, start up from an external drive, or else use the technique in Step 1b, 1c, or 1d to mount the internal drive and delete some files. According to Apple documentation, you need at least 9 GB of available space on the startup volume (as shown in the Finder Info window) for normal operation.
    Step 3
    Sometimes a startup failure can be resolved by resetting the NVRAM.
    Step 4
    If you use a wireless keyboard, trackpad, or mouse, replace or recharge the batteries. The battery level shown in the Bluetooth menu item may not be accurate.
    Step 5
    If there's a built-in optical drive, a disc may be stuck in it. Follow these instructions to eject it.
    Step 6
    Press and hold the power button until the power shuts off. Disconnect all wired peripherals except those needed to start up, and remove all aftermarket expansion cards. Use a different keyboard and/or mouse, if those devices are wired. If you can start up now, one of the devices you disconnected, or a combination of them, is causing the problem. Finding out which one is a process of elimination.
    Step 7
    If you've started from an external storage device, make sure that the internal startup volume is selected in the Startup Disk pane of System Preferences.
    Start up in safe mode. Note: If FileVault is enabled, or if a firmware password is set, or if the startup volume is a Fusion Drive or a software RAID, you can’t do this. Post for further instructions.
    Safe mode is much slower to start and run than normal, and some things won’t work at all, including wireless networking on certain Macs.
    The login screen appears even if you usually log in automatically. You must know the login password in order to log in. If you’ve forgotten the password, you will need to reset it before you begin.
    When you start up in safe mode, it's normal to see a dark gray progress bar on a light gray background. If the progress bar gets stuck for more than a few minutes, or if the system shuts down automatically while the progress bar is displayed, the startup volume is corrupt and the drive is probably malfunctioning. In that case, go to Step 11. If you ever have another problem with the drive, replace it immediately.
    If you can start and log in in safe mode, empty the Trash, and then open the Finder Info window on the startup volume ("Macintosh HD," unless you gave it a different name.) Check that you have at least 9 GB of available space, as shown in the window. If you don't, copy as many files as necessary to another volume (not another folder on the same volume) and delete the originals. Deletion isn't complete until you empty the Trash again. Do this until the available space is more than 9 GB. Then restart as usual (i.e., not in safe mode.)
    If the startup process hangs again, the problem is likely caused by a third-party system modification that you installed. Post for further instructions.
    Step 8
    Launch Disk Utility in Recovery mode (see Step 1.) Select the startup volume, then run Repair Disk. If any problems are found, repeat until clear. If Disk Utility reports that the volume can't be repaired, the drive has malfunctioned and should be replaced. You might choose to tolerate one such malfunction in the life of the drive. In that case, erase the volume and restore from a backup. If the same thing ever happens again, replace the drive immediately.
    This is one of the rare situations in which you should also run Repair Permissions, ignoring the false warnings it may produce. Look for the line "Permissions repair complete" at the end of the output. Then restart as usual.
    Step 9
    If the startup device is an aftermarket SSD, it may need a firmware update and/or a forced "garbage collection." Instructions for doing this with a Crucial-branded SSD were posted here. Some of those instructions may apply to other brands of SSD, but you should check with the vendor's tech support.   
    Step 10
    Reinstall the OS. If the Mac was upgraded from an older version of OS X, you’ll need the Apple ID and password you used to upgrade.
    Step 11
    Do as in Step 9, but this time erase the startup volume in Disk Utility before installing. The system should automatically restart into the Setup Assistant. Follow the prompts to transfer the data from a Time Machine or other backup.
    Step 12
    This step applies only to models that have a logic-board ("PRAM") battery: all Mac Pro's and some others (not current models.) Both desktop and portable Macs used to have such a battery. The logic-board battery, if there is one, is separate from the main battery of a portable. A dead logic-board battery can cause a startup failure. Typically the failure will be preceded by loss of the settings for the startup disk and system clock. See the user manual for replacement instructions. You may have to take the machine to a service provider to have the battery replaced.
    Step 13
    If you get this far, you're probably dealing with a hardware fault. Make a "Genius" appointment at an Apple Store, or go to another authorized service provider.

  • My imac has a gray screen when waking it up from sleep mode. about 9 months ago, I installed OS X Maverick.

    This is the second time this has happened, since installing OS X (9 mos. ago). (I can't recall the fix from the last incident.) Upon waking the pc up from sleep mode, I get a gray screen. Nothing works except using the Command and P & R keys to get to "reinstalling OS X", to no avail. What do I need to do to get it back to normal?
    My imac is a 21.5", mid 2011 item.

    Those keys do not reinstall OS X. To do that:
    Reinstall Lion, Mountain Lion, or Mavericks without erasing drive
    Boot to the Recovery HD:
    Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.
    Repair
    When the recovery menu appears select Disk Utility. After DU loads select your hard drive entry (mfgr.'s ID and drive size) from the the left side list.  In the DU status area you will see an entry for the S.M.A.R.T. status of the hard drive.  If it does not say "Verified" then the hard drive is failing or failed. (SMART status is not reported on external Firewire or USB drives.) If the drive is "Verified" then select your OS X volume from the list on the left (sub-entry below the drive entry,) click on the First Aid tab, then click on the Repair Disk button. If DU reports any errors that have been fixed, then re-run Repair Disk until no errors are reported. If no errors are reported then click on the Repair Permissions button. When the process is completed, then quit DU and return to the main menu.
    Reinstall Mountain Lion or Mavericks
    OS X Mavericks- Reinstall OS X
    OS X Mountain Lion- Reinstall OS X
    OS X Lion- Reinstall Mac OS X
         Note: You will need an active Internet connection. I suggest using Ethernet
                     if possible because it is three times faster than wireless.
    COMMAND-OPTION-P-R keys resets the PRAM. OS X keyboard shortcuts.

  • IMac Freezes on blue screen during startup after installing itunes 9.2

    I let iTunes update to 9.2 today on my 27" iMac quad and when it restarted itself it froze on startup at the blue screen. The blue screen switches between two different shades but never exits that loop. I CAN boot in safe mode (which is what i'm doing right now).
    Thus far i've tried:
    - reinstalling itunes
    - resetting my pram
    - uninstalling itunes
    - removing itunes startup app
    I still cannot boot normally. Help!

    You might try booting from your install CD and running disk repair in Disk Utility.

  • IMac Freezes at white screen during startup

    Hello,
    I was off of my iMac for an hour or two so my screen saver when on.  I went to wake the computer and it was frozen.  I tried using the keyboard and mouse to wake up the computer from the screen saver, but it would not work, so I powered the iMac down manually from the button on the back.  I let it sit for 15 minutes, then I tried to start the computer up again.  Now at start up, I get to a blank white screen with the spinning moving pin wheel, and that is it.  Any suggestions?

    You could try to use SafeBoot mode on startup, essentially you'd hold the Shift
    key down on startup, perhaps you may need to login after waiting quite awhile,
    then continue holding the shift key down until you see a traditional desktop.
    And then use Disk Utility to verify HDD, & repair disk permissions.+ Restart.
    Or if you have a system install-restore DVD, boot from that and have the
    Installer's version of Disk Utility check verify repair the hard disk drive.
    It can also repair disk permissions, too, from the booted version of D.U.
    Then when it is done, choose the startup disk from installer menu options.
    The DVD should eject, but if not, it should be ignored as a boot volume
    after you've chosen the Mac HD as a boot system.
    PS: If your computer is now running a system later than Snow Leopard,
    where no DVD would be needed if it has a Recovery partition in the HDD
    then you could see about booting into Recovery (command + R) to access
    the later system's OS X Utilities, and choose Disk Utility to check/repair, etc.
    These may help.
    Good luck!
    edited

  • IMac Freezing Up/Blue Screen

    If this was posted in the wrong forum, please move.
    Sunday evening, my iMac G5 started freezing up a lot. I was forced to keep restarting my computer. Originally, I thought it was due to Firefox 3 seeing how I just downloaded it a few days prior. I ended up deleting Firefox, but the problem only got worse. After looking online and trying such things as repairing the permissions, I gave in and did a disk install (while keeping network settings and files). Disc 1 install went fine, but everytime I tried to install the contents of disc 2, it would freeze. I decided to just attempt to do a full re-install losing all of my contents of my computer. Finally, while starting in Safe Mode, I was able to finish installing disk 2.
    However, now I can't even get on my computer without it going to a plain blue screen (NOT the default wallpaper) and either the spinning pinwheel (I assume it was freezing up) or a curser. There wasn't any dock or any icons most of the time. Occasionally, it does take me to my default wallpaper, but it freezes up before the entire dock shows up.
    Everything seems to work fine in Safe Mode, but trying to log into the normal mode always gets me to the blue screen or a frozen screen.
    My S.M.A.R.T. said that it was verified. Meanwhile, through the install disk I have been in Disk Utility and I have ran a disk repair and repair permissions. The problems continues though.
    I've presented my problem to another message board which had the general thought that my HD was dying and I was in need of a new one. However, I have conflicting reports as another person is saying that my HD is not dying, especially considering the S.M.A.R.T. was verified.
    Right now money is tight, so I can't just easily go out and buy a new HD. So I'd like to try anything before giving into that. Any help would be greatly appreciated.
    Details:
    17-inch iMac G5 (Ambient Light Sensor)
    1.8 GHz PowerPC G5 processor with a 17-inch screen
    Owned since Sept 2005

    Hello and Welcome to Apple Discussions ...
    If you haven't tried this yet... grab your system restore disk(s). Make sure your Mac is shut down. Now, while holding down the C key, press the power button and insert the disk. Keep holding the C key until you see the Apple logo on the screen. Now, an Installer window will open... ignore that and go up to the Menu and click Utilities/Disk Utility. DU will launch. Select MacintoshHD in the panel on the left, make sure the First Aid button is selected and click Verify Disk. I'm not talking about the S.M.A.R.T status.. this is going to check to see if there are errors on the drive. If DU reports errors, click Repair.
    Now, you can't use Disk Utility from the Application folder on the drive, you can only Verify and Repair the disk from Disk Utility on your restore disk(s). If Disk Utility reports errors but cannot repair them then you might want to look into a good disk repair utility such as DiskWarrior
    www.alsoft.com or TechToolPro www.micromat.com Neither are expensive.
    I understand how important your Mac is to you and I hope this helps.
    Carolyn

  • Imac freezing up and screen dissolve issues

    Hi all,
    My imac intel keeps freezing up for no reason and then won't let you force quit anything.
    It still seems to do things in the background like import cds to itunes and download items.
    Sometimes it also freezes and then the screen slowly dissolves to bright white and then restarts itself.
    Has anyone come across this before.
    The imac is about 6 years old.
    Thanks in advance.

    If your Mac ame with an Install Sisc, AHT hw test should be on one of them.
    One way to test is to Safe Boot from the HD, (holding Shift key down at bootup), run Disk Utility in Applications>Utilities, then highlight your drive, click on Repair Permissions, Test for problem in Safe Mode...
    PS. Safe boot may stay on the gray radian for a long time, let it go, it's trying to repair the Hard Drive
    Reboot, test again.
    If it only does it in Regular Boot, then it could be some hardware problem like Video card, (Quartz is turned off in Safe Mode), or Airport, or some USB or Firewire device, or 3rd party add-on, Check System Preferences>Accounts>Login Items window to see if it or something relevant is listed.
    Check the System Preferences>Other Row, for 3rd party Pref Panes.

  • IMac Freezes at Login Screen

    When I reboot my IMac, it gets to the login screen and freezes. The mouse will work, but I cannot enter anything into the password field; after a few minutes, I am able to start typing.
    Any ideas?
    Joe

    jcabaleiro wrote:
    When I reboot my IMac, it gets to the login screen and freezes. The mouse will work, but I cannot enter anything into the password field; after a few minutes, I am able to start typing.
    If you launch the Console utility you might spot messages around the time of the freezes that could explain what's happening.

  • IMac freezes on gray screen w/ logo & wheel ... help!

    Hey there guys. I was capturing footage in FCP today to an external Lacie and the comp froze. Hard restarted, but now comp won't boot past the grey apple screen. The wheel does come up, but freezes after 1 or 2 rotations. Resetting PRAM does nothing. Computer will start, shut down, restart, copy/delete files totally fine in safe mode, so it doesn't seem like a mount/HD issue. In safe mode, using disk utility to verify, no errors found. However, on restart after safe mode, problem reoccurs. I've installed no recent hardware or software. I don't have any startup programs that I know of. Is there some file somewhere I should be deleting that's causing this problem? Thanks!
    Message was edited by: mwaltz
    Edit: It's a 1 TB drive w/80GB remaining, 3.06 Ghz, 4GB DDR3 ram. Message was edited by: mwaltz

    HI and welcome to Apple Discussions...
    Boot back into Safe Mode and check for available disk space.
    Right or control click the MacintoshHD icon. Click Get Info. In the Get Info window you will see Capacity and Available. Make sure you always have a minimum of 10% to 15% free disk space at all times.
    In Safe Mode check for Login Items. Open System Preferences/Accounts then select the Login Items tab. Delete any files or apps you have listed there. And go to /Library/Startup Items. Move any files in the Startup Items folder to the Trash.
    Carolyn

Maybe you are looking for