Black screen where Champion Select should be

The timer ticked down, The Accept/Decline buttons came up, I clicked accept and then... nothing. The entire client (with the exception of the minimize, settings, and exit buttons at the top-right) was completely black. I waited and I waited and nothing happened, so I exited the client. Now I'm being punished by a leaver timer, waiting five and a half minutes to be able to jump in to another game.