I have a GTX 295 and for about 2 weeks now, after 3 -7 minutes of playing any game, I get a black screen and I have to perform a hot reset.
I've changed the video card with an old 9800 GT and also a GTX 560 and with both is working perfect. No issues.
I've tested my GTX 295 on a friend pc and is working perfect. No black screens issues on his PC.
I've changed the drivers but the issue is still there.