My father-in-law had a black screen after hibernating for 2 hours on his new Dell with Windows 7. I used Power Options to "turn off power" and "hibernate". As of 4 weeks later, the black screen has not recurred. I'll update his drivers over the Christmas holidays to see if that was the source of the problem. So, until somebody with more knowhow comes along, you might try changing the power options and updating drivers. I think there was also a post or two on other boards that said AVG could cause black screens. You could always uninstall AVG and try using MSE to see if that helps.