UNABLE TO TYPE IN GAME BUG

About 50/50 of my games I load into my game and then press enter key to talk to my team and NOTHING. I can't type. I know for a fact I am not chat banned because I am a very positive and encouraging player and I believe the game notifies you if you ARE chat banned. I also can't alt + Tab out of the game when this bug happens. I play fine and my pings work I just can't type.[sg-soraka] I just want to tell my adc he is great ... DOES THIS HAPPEN TO ANYONE ELSE?!?