I have an early 2013 rMBP and installed Windows 7 on it. I decided to put Windows 8 on it a while ago. Ever since I installed it, I get a black flash when I log in. Sometimes the screen will go black for a few seconds while working and come back. Is this normal? I did not notice any issues with Windows 7 when I had it installed. I have constantly kept it up to date (drivers, Windows, ...) but I still get this. It happens on the laptop display, and external displays. This does NOT occur in OS X.