Originally Posted by lanceomni

Personally I have never experienced it however I have heard of others getting having screen corruption like this when their machines freeze due to the memory. Using more than three and a half gigs of memory can cause freezes. There are some 64bit modified kexts to correct this issue. Just to narrow down the list of possibilities If you are not 100% sure this isnt a memory related issue I would boot using maxmem=2024 to limit OSX to 2 gigs of memory. See if you still get the issue.

You can also play some music in the background and try to get it to corrupt as these freezes generally result in complete system freeze. Monitors usually keep displaying the frozen state however keyboard, mouse and audio do not function.