happened with one of my 7850 drivers(12.3 i think). Its a driver related issue somewhere. whether its a graphics driver or like a missing intel/motherboard driver I dont know. I just avoided it and set it to never sleep.
Well I would do that, but for the sake of my electric bill I don't want to do that haha. But yeah before my 660ti iI had crossfire 7770s and I never had the problem. Crappy Nvidia driver I suppose