Do you have any devices plugged into your computer, like USB devices or a controller? If so, remove it.
If you don't, or if you see a black bar at the top of your screen/no heads up display/etc, you have the black bar bug. It is a well known glitch that makes the game unplayable for certain people at 22:00-24:00(AKA 0:00) poketime. It goes away after that, then happens again at the exact same time.
We aren't sure of an exact fix, but my personal investigations lead me to believe the bug is directly related to PC settings. Not sure how, though, so until then you'd have to just wait till the bug passes.