[Client]Champ Select not loading

I selected blind pick, pressed play, and eventually found a match which I accepted. My window changed to the standard boarder for champ select, but it was a plain black background with nothing clickable barring the X and _ buttons in the top right.

I had no way of closing the client and reopening it to get back into champ select, and have been given 5 min leaver buster.

It was not reproduced the next time I entered champ select.