Client closed after game and wont start up again

Pretty much that. After the game (ARAM) just finished and the results/honor screens are supposed to show up in windowed mode, nothing. the full screen game closed and that was it. nothing started back up, and there was no League on the task manager. whats worse is now I can't even start up League again. Ive clicked the desktop icon, tried to run it through command, nothing. The brief logo appears on the screen and nothing else follows..

Halp, I really dont want to make this a " Just uninstall and reinstall" thing as that takes ages, and (while it will probably work after) we havent really addressed the issue and will be able to prevent it again.