Game freezes in the middle of the match??

Out of nowhere my game will freeze, it'll do this almost every game too, no matter what I'm doing, I won't have any other programs running. I've tried reinstalling and repairing and that does nothing... I can hear the game but the screen is froze. I can ALT TAB but it doesn't go to another window it just hovers over another window. It wont let CTRL ATL DEL or task manage. I don't understand why it does this.. And my temps are not hot either. I've taken my computer apart several times to try and figure out what is wrong, even put in new video cards and still does it... Help? I've reported it to riots bug report but nothing...