[GAMEPLAY]Mouse stuck in upper left corner

Finished a game of ARURF, and couldn't see my mouse to click the Defeat button. Hit Ctrl-Esc, and my mouse was stuck in the upper left corner. Moving it made it shake wildly, but it wouldn't move until I Ctrl-Alt-Del to task manager. Even then, reentering League to try and finish the game caused it to happen again, and I ended up force quitting the game from task manager, which made the bug go away.

Done playing for tonight, but if it happens again tomorrow I'll edit the post.