HUGE freezes of the whole computer upon starting a game, manage to reboot... corrupted installation?

I queue up for a ranked game, after several people dodging I finally make it to the loading... and suddenly my PC stops working, my mouse doens't move anymore, when it moves it doesn't click, ctrl alt del doesn't do anything, then 3 mins later it works but then stopping processes doesn't do anything... I somehow manage to reboot my PC, and relaunch LoL. I am greeted with a warning that the data is corrupted and needs to be repaired.

...halp? Ranked game in progress and I'm already flagged by leaverbuster for having bad connection since mid September