It is the second time that my rMBP doesn't wake up from sleep. The only application that I've recently installed are Alferd and BetterTouchTool - Could it have something to do with that?
In addition it happened twice only after long time sleep of like 8 hours - if I sleep the machine now and wake it after 2 minutes it wakes up perfectly.
Do you have any ideas what can cause this? In Lion I had no problems.
EDIT: Apple released the following update
hopefully this will fix the problem.
EDIT: Nope, didn't help.
EDIT: I freshly installed ML again, which fixed my problem. I have added an answer below, please read it.