My rMBP has been having issues waking from sleep. About 20% of the time it acts like it isn't waking up and there is just a black screen. No keyboard lights or internal noises. When this happens on average it takes 2 minutes to wake from sleep but ranges from 60 seconds to 5 minutes. I have reinstalled the operating system with no restore from time machine. Also, I have done the different resets you do at boot up. I don't recall what they are called. Still no fix. The apple store was not much help. The tests they ran show everything is good. Also, because it doesn't happen every time I haven't reproduced it in the store. Any suggestions?