RE: Sleep and Hibernate modes get my Dell Mobile Precision 7510 to get stuck
Similar issues with my son's 7510 (but better than Win 7).
The odd one was:
on wakeup, the built in screen was blank (but backlight on), plugging into HDMI then worked.
Also, it would work if the lid was closed and then reopened.
He has set the lid action to 'nothing' for now.