Critical Error (crashing the game)

Hi, i have been recently getting this crash from league of legends in every games i play. this happened after the latest update. I can play the game for good 5 minutes and then everything would freeze but the game sound will be able to be heard. i can't do anything with my computer afterwards. i have to sleep my computer and then turn it back on, which makes the game goes completely black and i wont be able to see anything... for this issue, i've been banned for 5 games (10 mins) for quiting the game and as a punishment which i never intend to do. please help me!