Graphics problem on iMac G5 w/ iSight.

Question

I just tried installing a 1GB RAM stick in a 17" iMac G5 (iSight). The machine has 512MB of RAM (the standard), and a 1.9Ghz processor. It is running Mac OS X 10.5.7.
My friend, who owns the iMac told me she'd been seeing some weird graphics artefacts and had been having several lock-ups on the computer which required a forced restart to fix. I didn't know what to make of this and said I'd check it out when I went to install the RAM for them.
The problem alarmed me - rather than a few stray black lines that I had been told about, I found all of the following issues.
1. Black / White or Transparent lines on windows and toolbars. These were particularly predominant on menus and other semi-transparent parts of the screen, but also occurred on solid windows - such as Safari.
2. Blank screen - the screen would just go blank after a few moments.
3. Screen freezes - everything on screen would stop other than the arrow. Sometimes this would stick as an arrow, or sometimes as a beachball.
4. A really strange phenomena when I opened a browser page and suddenly the left of the screen slowly faded to black, while the right went white. This went in increments as I watched with the image of the desktop distorted behind it, burning out.
To try to fix the problem I took the following steps:
1. Reinstalled Mac OS X 10.5.7 Combo Update. This had no effect.
2. Repaired permissions. (I didn't expect that to help anyway)
3. Tried booting into a second user account on the computer (again, all the same problems were there - even worse on the other account in fact.
4. Unplugged all peripherals (no effect)
5. Removed the 1GB memory stick I had just installed - this appeared to fix the issue and I thought that maybe this was causing it. However, after a few minutes of normal operations, the problems all came back.
Just to clarify - the problems apparently started a week or so ago (this might coincide with the owner installing Mac OS X 10.5.7, but I can't be sure), at this point the computer only had its built-in 512MB RAM. With the additional 1GB RAM that I installed, the problems seemed to be worse. I know there is nothing wrong with the RAM as I had been using it in my iMac G5 up until this point.
I initially suspected the problem was the graphics drivers - as the problem occurred after upgrading to OS X 10.5.7, though I wondered if the problem could be the GPU itself?
However, I am now wondering if it's a RAM issue as additional RAM makes the problem worse - would having more in the computer change the way that the internal RAM is being accessed and mean that the end addresses of the built-in RAM are being accessed more quickly when additional memory is installed?
I was unable to find out if the machine would work alright if booting from the Leopard or original install Tiger DVD - as I didn't have time to check these.
Please advise me what I can do to diagnose the problem further, or what the owner can do to fix the problem.

Answer 1

"I will have to dig out my copy of Leopard or the original installer for my iMac G5 (w/iSight) as the owner doesn't know where her copies have gone! Maybe trying these will help find a solution"
You cannot use the System DVD/CDs from one Mac to another. The System discs are _+machine specific.+_ You may cause further damage if you use it.
You can get replacement System Install & Restore CD/DVDs from Apple's Customer Support - in the US, [phone] - for a nominal S&H fee. You'll need to have the model and/or serial number of your Mac available.
If you're not in the US, you may need to go through the regional Apple Store that serves your location to find the contact number. Here's a list of links to all of those -
http://store.apple.com/Catalog/US/Images/intlstoreroutingpage.html
However, you can try using a purchased retailed Leopard DVD.
=================
Try the following:
Mac OS X 10.4 Help-My Dispay Doesn’t Look Right
If the above is of no help then you will need to do the following:
System Preferences>Display>Display
Check the Colors & Brightness settings.
My Color setting is set to Millions which I believe is the default setting.
Now click on the Color button.
Check Display Profile
Is Show profiles for this display only enabled or disabled?
If necessary click on the Calibrate button & do the necessary.
Now in the bottom right corner, click on the purple button w/the black ? mark in the middle. This will bring up the help window.
Midway down, click on the Colorsync Utility link.
The next window should be Profile First Aid.
Read & follow the instructions/details of About Profile First Aid: & do the necessary to Verify & Repair.
If the culprit is the video card, you will need to take the computer to the nearest AASP or Apple Store for repairs.