Hey man, I just registered today but all I did was google your problem and came up with a user with a similar one and this is what he said:
"Hi, I also had this problem, and it drove me CRAZY!!!
but, I found the solution after ravaging random forums for 2 days. I believe the problem was that ATI graphic cards think that they are overheating, and the VPU recovery kicks in for no reason, and then shuts down the computer because it doesn't want to damage the card.
there was a patch/file released that fixed this problem, all you have to do is download it and d-click the file so it goes into your registry. since I have done that my comp. has been goin strong for 3 days, instead of 1-2 hours like before.
http://www.amd.com/us-en/Processors/...1_2367,00.html
if it works, great! and I feel good about helping someone.
if it doesn't sorry and I hope you find the real problem soon"
Let me know if that helps. I am also having video card troubles so I can empathize with you.
Cheers,
Josh