Try uninstalling, totally cleaning off the driver, rebooting, then reinstalling your driver.
I had this problem in Demigod with my nVidia card, but the problem was a driver issue. I change driver versions and had no problems.
Also, is your card overclocked? Perhaps it's clocked too high. I've had the problem too. My card is factory OC'd, but when I tried to push it even further, I'd get blue screens once in a while in games.