Graphics issue

i own a pc with i7 920 and gtx 295....All ran well until a few days ago when the display would actually go black for a few seconds and return back with "Nvidia display driver kernel mode stopped working and successfully recovered"....i am using windows 7 RC...though this has happened before but not as frequently as now which is every 10 min or so while watching videos or playing games....it is pretty irritating...i also have XP and in that too when playing some games the display would freeze and the game will start again with the textures all over the place this will happen every few minutes....but i dont get any of these issues when working in 3D apps like maya or max no matter how much the screen is cluttered....i checked the card temperature which is always normall between 70C and 80C.....i dont get any artifacts on screen and i have not got any BSOD with regard to these issues.....Its pretty mysterious to me....Please help me out with ur thoughts guys....

i have a coolermaster 750w psu

sorry for the mistake its coolermaster 850w real power pro