Same problem here, after the game concluded (we had a yasuo who fed then afk'ed, so we were forced to /ff ), I was stuck in the "skip stats" screen, which I did after waiting 2-3 mins.
After that I got into the lobby as usual, picked my roles, but upon clicking the "find match" button, I was greeted by a popup message saying an error had occured and to try again later.
I decided to logout then log back in, and upon reconnecting, it automatically launched the game proper, then got stuck in a black screen, then gave out the timeless message saying to check if there was a firewall problem or other (nice try riot).
I used alt-f4 to close the black game window, which put me back to the "reconnect" screen.
Which is quite a problem, since the game has ended already and is even in my match history.
So it seems the server considers I am still in a game that's already over, and tries to reconnect me to that ghost game. Which also prevented me from starting a new game, as the server still thinks I'm in my previous one.
As usual, good job riot.