if it's stable under furmark, I think it might be a software issue.
when you downloaded and installed the latest drivers earlier. did you do it the quick way? if yes, try completely removing nvidia drivers and re-install it again.
(your screen might not come back on after the uninstall phase... i waited a good ten minutes before resetting my computer, it loaded window's default drivers. I then installed nvidia's driver. but this did fix the issue for me.)
also update directx if its not up to date.