I was having trouble with keyboard keys not working in dosbox. I was playing "Star Wars: Dark Forces" with a gamepad along with a program called "AntiMicro" to assign keyboard keys to the gamepad and while I was playing the game certain keys stopped working, for example I couldn't bring up my map using the [TAB] button. I also couldn't leave dosbox with the windows key. I figured one of the keys got stuck in on mode and while I kept trying to press the key to get it to work eventually a dark screen with a white keyboard layout appeared and asked if I wanted to change an event. I said exit without doing a thing and everything seemed to work fine until the problem repeated itself.
Sometimes I could hit [ALT]+F4 and that sometimes worked but something was causing dosbox to lock keys in place. I think it has something to do with some kind of key combination that I pressed and something to do with that black screen with the white keyboard. The problem eventually fixes itself but it kept repeating and it was getting annoying. It wasn't anything to do with "AntiMicro" because the keyboard also didn't work.