Game Freezed when BP for rank

The game sometimes freezes and unable to reaction for any click. When I relog in, it showed me cancel a game and forbid me to start next game, and also reduced my rank points. Sometimes it freezed after my pick, then I can wait for game starting and reconnection. In this case it doesnt matter. This also happens on computers of my friends. We use Alienware, and OS is Win 8/Win 10.