I'm new to the forums, I'm not quite sure how to do that... Do you need specific files?

I'm using a USB stick for data storage, and up until two days ago it worked like a charm. Now when I'm in-game and try to exit retroarch (via hotkey or menu command, same result), I just get a black screen instead of returning to the games list. I can't access the main menu, there's just a completely black, unresponsive screen, forcing me to reset the system.

Does anybody know a possible explanation? Thanks in advance!