Kinda hard to tell from that screenshot, as I am not familiar with the game. I assume those bars are not supposed to be there?
I don't see any pixelation, so I don't think it is an overheat problem, but might as well rule that out first. Open up the case and aim a house fan at the insides. Does that lessen the problem?
Has this card ever worked for you? In other words, is this a sudden new problem, or a problem that has always happened since you popped that card in?
If it is a new problem, then it's likely not a driver issue. Either your video card ram is dying, or your PSU is dying (not giving the graphics card enough power).
If it is a problem that has always happened, then it may be a driver issue. Have you updated your board's chipset drivers as well?