Ive been having a recent problem with computer crashes while playing some of my newer games (NBA 2K11, MLB 2K10, Assassin's Creed cheap nike air max mens shoes,Street Fighter 4). When the comp shuts down it stutters for half a second and then turns off, like someone flipped the power switch. Older games run fine. Throughout all the research ive done most people are saying power supply is the likely cause, but i have a nice 650w corsair power supply that i got 1 year ago. Im leaning more towards overheating issues but im not really sure, any advice?

Note: Also, I updated my video card driver not that long ago but it was causing the display to randomly pixellate while gaming and was very unstable black and pink air max 97. I reverted back to the original driver that came with the card (ATI Radeon HD 4870) when I bought it, no problems with pixelatting since.

6 GB DD2 RAM66C is my idle temp I think, it was the number i saw when i was in the bios menu. My comp is set to shutdown if the CPU reaches 85C. I have already cleaned out and reseated the heatsink a couple times, same result. The heatsink is 1 year old, the processor is about 3 years old. Im not overclocking nike air max skyline women sliver.