(client) cant click in the client/with champion picking

Sometimes in the client or when im choosing a character, i cant click on anything. The buttons do light up but it wont trigger anything. If i restart LoL it is over. But it is really bothersome when your in your promo's and you dogde because you cant click on a champion....

Is there anyone who encoutered the same problem? Or knows why this happens.

Kind regards

MadOldCrow