Random dot pattern flashes on screen when I wake iMac from sleep...

I've never seen this on a Mac before, but when I wake this iMac, the screen momentarily flashes a grid of green, blue, and purple dots on a black background. Some are circular outlines, some filled-in dots. Wish I could describe it better, but it only shows up for a moment! Anyone seen this before?

You might want to read/post about this here: http://discussions.apple.com/forum.jspa?forumID=1114

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My Mac shows a black screen when it wakes up from sleeping. How can i fix this?

Sometimes my Mac goes to sleep by its self and when i try to wake it up i get a black screen how can i fix this?
-Isaac Hatfield

By trying some of the suggestions mentioned in the More Like This threads.

Does anyone know what to do when a apple mac book pro screen won't wake up from sleep?

Does anyone know what to do when a apple mac book pro screen won't wake up from sleep? I have tried to restart it and it still won't come on.

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Thunderbolt ethernet not working when computer wake up from sleep.

thunderbolt ethernet not working when computer wake up from sleep.
it will not happen in Mountain loin.

I had this problem on SL and on Lion as well, and it occures for WiFi and Ethernet connections.
In fact the internet connection was not broken as I could ping the destination usin the IP (not DNS name).
In this case the problem was related to mDNSResponder task which handles all dns queries.
It was the most frequent problem in my day to day work with SL and now Lion. It was never fixed by any patch from Apple. I tried almost all voodoo including fresh install, all possible config changes - no solution.
The only version with no problems related to network was 10.5.8. All the other versions had issues of different kind (WiFi instability (lost signal), DNS problems (for wireless and wired connection) sometimes associated with machine sleep and wake up and sometimes with no reason.
QUESTION: Is your problem independent of the access point / router you connect to.
I must say networking was (and still is) the weakest part, besides the other OS X weaknesses I experienced during 4 years of OS X usage.
No problems in the same network with Linux or Windows beeing ran natively on my iMac So hardware is OK.
Software is of poor quality. Not much more to say in this matter.
I found a very interesting article dated 1996 about programming which I think is still valid.
Link to the article: http://www.fastcompany.com/magazine/06/writestuff.html
Below the fragment (with some connection to Apple)
Software is everything. It also s***s.
"It's like pre-Sumerian civilization," says Brad Cox, who wrote the software for Steve Jobs NeXT computer and is a professor at George Mason University. "The way we build software is in the hunter-gatherer stage."

Random blue/red flash on screen when exiting apps

Hi,
I have an iphone 6 64gb with ios 8.1. I encounter a weird blue and sometimes red flash on screen when exiting app (specific to galaxy empire only). It looks like the blue/red screen of death but just a very quick flashing. so far no other problems occured but it sokehow makes me uncomfortable especially the phone is only less than 3 weeks old. Is it a hardware problem?

You might want to read/post about this here: http://discussions.apple.com/forum.jspa?forumID=1114

Internet connection does not work when Macbook wakes up from sleep

I recently installed MAC OSX LION. After that whenever the macbook pro wakes up from sleep, the internet connection does not work. I get a message 'DNS lookup failed'. I have to Turn off the WIFI and turn it back on every time. Has anyone come across this?

Same problem here. But I am afraid it has nothing to do with Safari because I don't even have Safari open. When it wakes from sleep, it has no internet connection and i cannot get me mail unless I shut wifi off and then back on. This happened back at the start of Snow Leopard too and it was something Apple eventually fixed.

Flashing screen when awakening my mac from sleep

Help: What can I do to fix my screen issue-- It flashes for the first 20 seconds each time when I awaken my mac from sleep mode: Thanks!
(mac pro 2007 intel based)

Thanks, Linc. I was worried that since this was a refurbished computer, it was dying again. Makes sense, although alittle annoying that nothing really warns you this is happening. I almost cycled power the first couple times it happened, thinking it was stuck while waking.

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.

Tv/monitor resolution switches when mini wakes up from sleep

I have a mac mini c2d with intel graphics on leopard 10.6.2 connected to a sony 46w4100 tv. After updating to 10.6.2 when it first came out (i had used 10.6 and 10.6 aswell before this and this problem did not occur) i immediately noticed an issue. when i put my mac to sleep and wake it back up, instead of outputting to tv as a media player so that i have access to detailed picture settings, it reports itself as a PC thus limiting what i can change and the picture quality. i mainly use this as an HTPC, and its a problem since wiht my tv(not sure if ohter tv's have this), settings for connecting to dvd/blueray player/satellite receiver are extensive and picture is sharp, vs connecting it to computer where you only have the option of text and video and the video is not as vibrant or sharp. if i shutdown the mac and start again ,ir goes back to normal, but if i sleep and wake up, this behaviour occurs. 10.6 did not have this problem neither did 10.6.1. infact with 10.5 my mini always reported as PC thus i had limited options but with 10.6 i was happy to notice it was fixed.
is there someway to avoid this other than just ensuring my mac never goes to sleep (wasteful since its not in use most of the day). is anybody else seeing this issue and do you think this is a bug or aws the 10.6 and 10.6.1 behaviour a "bug" that apple has decided to fix.

also note the topic may be a bit misleading, when the mini wakes from sleep it is still outputting 1920x1080 so resolution does not change. when i first turn on mac, the sony tv shows 1080p output, full screen, etc etc and all the settings. when i wake from sleep and turn tv on, it doesnt have any any of that info so it doesnt even tell me its 1080p but it is.

How do I stop my computer from going to the standard user account when I wake it from sleep

When I wake my computer from sleep it logs on the standard user account. I need it to go to the administrator account so I can log on to that .

Hello rnash62. I understand you'd like to automatically log into your Administrator account when waking from sleep.
What notebook do you have? Please identify it by the product number. This document can show you where it is located.
What version of Windows are you running?
Once I have this information I should be able to provide you with instructions.
I hope you have a great day and an amazing weekend!
Please click the white star under my name to give me Kudos as a way to say "Thanks!"
Click the "Accept as Solution" button if I resolve your issue.

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My Lenovo Yoga 11s does not wake up after putting it to sleep. I will press the power button multiple times, but the screen stays black. To turn it on I have to press the power button for 10 seconds so it completely shuts off, then I push the power button to turn it on. However when I do this all my tabs and windows are closed, which is very inconvenient.
Please help me find a solution!!!!!!!!!!!!!!!!!!!!

hi Parabola,
Thanks for Posting
Can you try checking this step
http://www.dummies.com/how-to/content/activate-hybrid-sleep-on-windows-pcs.html
Turn ON the Hybrid sleep and see if that fixes the issue,
Hope this helps
Cheers!
Did someone help you today? Press the star on the left to thank them with a Kudo!
If you find a post helpful and it answers your question, please mark it as an "Accepted Solution"! This will help the rest of the Community with similar issues identify the verified solution and benefit from it.
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Early 2008 MacBook Pro screen black wont wake up from sleep won't restart

A few months ago my screen would flicker and freeze every so often. It hasn't done so in a while.
Today, I was working, and it was working fine. I shut it (in sleep mode), and a few hours later I went to open it and work again and the screen wouldn't come on, and from what I can hear wont come back on. I've held the power button down and the sleep light will go off, but if I hold it down again, you can hear the computer do something, but does not chime as if it were starting up. The battery is fully charged, I've taken it out, let it rest, and put it back in, and its still not working. Twice now I've held the power button down and all I get is this deep loud buzzed beep.
Any ideas what this could be???

MacBook Pro: Distorted video or no video issues

Screen problem after wake up from sleep

About three weeks ago I posted a problem with the display coming back to life after waking up from sleep. I said this happened after the 10.5.2 update. This turned out to be not quite accurate. I actually ran all the waiting updates, so I really don't know which one to finger.
Today, I again ran the 10.5.2 update by itself. Everything is fine. Software Update then identified seven more updates to do, some familiar, some not. I have done all except one, one at a time, and have had no problems with the display coming on after the computer wakes up.
One more to go: Leopard Graphics Update. This is v1.0 for this update, and here is my question:
Before I run this update, and face another possible day-long re-install and re-update session, has anyone experienced the problem with the display remaining dark after running this update? I hate to do the update just to see if it causes the problem if there is some information kicking around about this.
Many thanks again for any help or comment.
Jim

Hi rohitgu,
Welcome to the Apple Support Communities!
I would suggest using the following article for troubleshooting the display flickering on your iMac. I would specifically Reset the system and Reset the resolution. I know you have done some good troubleshooting already. Have you reset the SMC as well as the PRAM? I also see that you checked the resolution on your computer, but have you started in Safe Mode and adjusted the resolution? Please use the following article as a reference.
Apple computers: Troubleshooting issues with video on internal or external displays
http://support.apple.com/kb/ht1573
Reset the system
You can reset the Mac's parameter RAM and SMC.
Reset the resolution
Start by resetting the Mac's parameter RAM. If the display does not come up, was previously set to an unsupported resolution, and still results in no video:
Start up in Safe Mode.
From the Apple () menu, choose System Preferences.
Choose Displays from the View menu to open the preferences pane.
Select any resolution and refresh rate that your display supports.
Restart your computer.
I hope this helps,
-Joe

Firefox not working when PC wakes up after sleep but Chrome is working.

When laptop wakes up from sleep, already opened tabs in Firefox are not getting connected to internet. After two minutes opening a new Firefox window is connecting to internet. But this problem is not happening with Chrome.

When you are doing this, set the drive to never sleep, slider completely to the right and display sleep to something like five minutes. Or just hit Control-Shift-Eject, to sleep the display. Uncheck "put the hard disks to sleep..." That said, the firmware on the externals may be spinning them down. But this shouldn't be happening if they are being written to.
System Preferences> Energy Saver.

Hey my air's screen is mess when it comes back from sleep. It is full of horizontal colorful lines. However, it becomes ok when I restart it. What's wrong with it?

Hey my air's screen is mess when it comes back from sleep. It is full of horizontal colorful lines. However, it becomes ok when I restart it. What's wrong with it?

Resetting PRAM may help.
Reset PRAM. http://support.apple.com/kb/PH4405

Random dot pattern flashes on screen when I wake iMac from sleep...

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