I just noticed yesterday after installing a new AMD driver 17.7.2 that I have been experiencing issues where any game that uses UE4 is a black screen when I have it set as windowed or windowed full screen mode. But I can play the game fine if I have it in full screen mode.
I first tried the game ARK - first thinking maybe it was that game itself, but then I tried another game that used UE4 and had the same thing happen. It works when it is full screen, but a black screen when windowed.
It seems to only occur on UE4 enabled games, I can play UE3 games fine in both windowed/fullscreen.