Game crashs from nothing.

Hello. I have a problem and i dont know if its a bug or some other problem BUT.. When i play league its fine. And sometimes happends really strange bug/thing.. Im playing. Its ok 10 minutes ok. 16 minutes im in great fight that we've won. and than... Game freezes and drops to windows.. BUT! I still have mouse icon from LoL in windows and i can hear sound from LoL but i cant click on anything... It happens to me every 5-6th game.. And now im in Low priority queue cuz it recognizes me as AFKer or Leaver.. even when i connect back playing... Im really mad and confused. I dont play on main account cuz of that problem.