Can't select my champion

Some times when starting a game form a premade lobby (not team builder) after accepting the game found pop; up the screen will revert back to the lobby screen or home screen, however i will hear the champion select music and timer but be unable to pick causing me to rack up leaver penalties. This has been happening a lot and started around the time the New rift was being shipped to the live servers. I would appreciate some kind of assistance if it's a problem caused by my hard ware or a fix if it is a problem with the client code.