OC'd 6970, fine except for one game?

I have been running my 6970 at the max clocks in MSI afterburner 950/1450, did some extensive testing (just playing a lot of just cause 2 max settings mostly but also played other games too like metro 2033 and crysis, warhead and crysis 2). Today I decided to play a bit of Witcher 2 and almost immediately I started to notice these white "flashes" occurring on screen and then eventually the ground will all of a sudden raise up to my characters waist, basically it is all screwed up. I assumed it was either the core or mem clock too high, so I fiddled around and I think I got it to stop, currently I am at 940/1435.

What I am wondering is does it really make sense that only one of my games would be causing instability, and not all of them? The temps on my 6970 never go above 73C so I know the temps aren't the problem. Even playing a game like just cause 2 for hours on end and then Witcher 2 for like 15 min?

Thanks