I was given a MacBook Pro. Its one with the defective X1600 GPU (Thanks ATI!). I have been doing buckets loads of research and no one has a fix. Heat is the biggest factor, but it seems that the ATI drivers are an issue also.
Anyway, seems I have been the only one to come up with a fix that has worked for one machine so far. Been pushing it very hard too. No issues at all. If anyone has one of these and want the fix, let me know! I am interested to see if it works on other machines. It does require taking the computer apart to pull the internal battery to clean out the PRAM. A PRAM reset is not enough.