Mac client freezes in champ select

When I join a game or try to select a champ the client will freeze in and when it unfreezes I am returned to the lobby for not selecting a champion. But I couldn't select a champion because the client won't let me. I can't advance in a series because every "unintentional dodge" due to the frozen client counts as a loss. Really annoying.

I have tried doing a full repair and that didn't help. It isn't my internet connection.