I ran for a while on my gtx 460 with older drivers, but when I upgraded a couple of weeks ago (might have been a beta driver, don't remember) it started. I just downloaded the new drivers from the 24th today when I finally installed my gtx 480, but I've been using the computer for more than just browsing most of the time and haven't had the restart issue. Also, iirc, the issue is mostly happening on gtx 460 cards with the new drivers.
edit: I see that you have a 560 ti, I think that 560 was also mentioned as having the issue.