Game won't launch.

I go through champ select, and the loading screen simply doesn't come up. All I'm given is this "Game is still in progress" screen. I tried switching off my firewall. Interesting thing is, when I restart my computer or exit the client and relog many, many times, it will sometimes go into the loading screen and I can play. However obviously by that point, I'm late to the match. Starting to seriously bug me. Help would be much much much appreciated.