Apevia 700w PSU
Visiontek 4870 512MB (Reference cooler)
G. Skill 2GB DDR2 @ 800MHz
Asus P5E Mobo
Intel E8400 @ 3GHz
Western Digital 320GB HDD
A few months ago, I noticed that recent titles (Mass Effect 2, Bioshock 2, Left 4 Dead 2) would freeze up on my computer. The screen would freeze and reveal white bricks or something. After a few minutes, the screen would sometimes return to normal or crash outright. I looked at the catalyst control center and found that my GPU idles at around 65C!
I wish I could say it was just games that were freezing. Often times, Firefox 4 will crash out of nowhere and the Hammer SDK will sometimes do this as well. Might I be looking at a faulty PSU and/or GPU? Is there any more information I could provide to determine which might be the case?
A 700w PSU should be way more than enough to power all you have, I have a i7 990X and gtx550ti 1gb GDDR5, and I am running it on a 600w power supply I previously had to replace my GPU because of freezing when I did it solved the problem. I would say it is your GPU but I could be wrong its a tough question.
take the covers off the case and blow a big ol, box fan into it while its running, see if that drops the temp and changes anything. if not maybe the gpu already damaged? in my experience bad crashes like you're describing usually meant hardware failure.
(always the best bet to try a diff. card if you have one, or try that card in another comp)