Same symptoms here...runs flawless with everything on ultra, but after a minute or two screen goes black after reverting to desktop for a second, I hear the sound running and crysis 2 exe doesn't respond anymore.
Nvidia 580 GTX with the Geforce 275.33 drivers, Win 7 64bit, 4 Gigs of Ram
Crysis 2 never crashed before, card isn't overheating.
Yeah, nice...