9800gtx overclocking

I was able to overclock the 9800gtx to 819 core 2048 shader and 1220 mem. It was stable for Furmark, as well as 3dmark vantage. Then, when i attempted to run farcry2, it ran a little bit then crashed. After that i decreased the clocks to 800 core, 2000 shader and 1200 mem. This time, while loading the game, i got a blue screen, talking about corrupt drivers, so i thought i'd try the game at stock. Same blue screen. I'm reinstalling the game and drivers, hopefully everything is alright. What i'm wondering is how did my drivers become corrupt if they did, and why was it stable in furmark and vantage, but not in farcry2?

Yea temps were far less for farcry than during furmark. The PSU should be alright, its a corsair 650w, actually i just got an RMA . I reinstalled the drivers, and farcry 2, and now everything works. But why would it be stable in furmark and vantage but not farcry2?

Could just be your drivers didn't like the overclock. Some driver versions are funny like that.