also, maybe try rolling back to the previous nVidia driver to the version you're using now. i was having issues with my new PNY GTX550ti with the newest (280.26) drivers, but i'm now back to 275.33 and no problems whatsoever. reading thru the various PC message boards, the general consensus is that the latest drivers aren't so good, and a lot of users had your exact problem. there's a few exceptions though, and they say the drivers are great. hope that helps.