Game Won't Load (Critical Error has Occurred Process must be terminated)

This is so not cool. Everything is fine at champion select, and then when the game loads, instead of the usual pregame window a new one pops up and says "Critical error has occurred, process must be terminated." I tried uninstalling and installing the game (and we all know how long that takes) and the same thing happened. I have two accounts and neither one of them works. I miss being able to play and now I can't.

Edit: for those who are experiencing the same problem, if you find a solution or it gets better by itself lml. Im terrible with computers.