leaver buster

It happens to me often and i dont know is it beacose of my computer or league launcher but sometimes when i start a game black screen just appear and my whole pc freeze. It happenned to me now and i lost ranked game beacose of that i tryed fast restarting computer but they remaked and i got leaver buster 5games 20min i really cant wait another 5 games beacose of this bugg that happen so if u can please just look into it and remove a leaver from me woud be good.[zombie-nunu-tears]