Unclosable Black Screen after champ select.

I've been trying to get into a game for a while now, and every time I try to get in I get a black screen I can't alt+tab or ALT+F4 out of. I end up having to reset my computer which I ended up doing three times to not success.

In fact, the game just boots up when I login, not giving the client a second to load up first before sending me to the black screen.

EDIT: This was not limited to just one game, I tried playing one with some friends and I ended up getting blackscreened again with no way to even play the game. I'm going to force a full reinstall.

UPDATE: Reinstalling did jack shit.