how long have you been running that video card??? any new upgrades done to the pc??? os?? and hardware.... need a bit more info.....
more often then not its a problem with the video card or the drives, try reinstalling the drives for that, or find an updated vertion of the drivers.
I know that I used to have issues with one of my fav games back in the day GTA3, it was because of the video card drivers, just rolled back to a previous version of the drivers, problem went away.... might not be your case...
but more info please.