Might be fixed now, but when playing yesterday with my mate (draft), he said that I had disconnected, which I hadn't noticed because I was in the loading screen. Soon noticed I couldn't click any of the champion cards, client wouldn't let me go to windows home page or anything at all. Was stuck, tried to go to task manager, even that refused to pop up.
Still managed to get into the game when it was 3 minutes in by logging out of my PC (just like task manager ctrl+alt+del), even though it gave me a scare because my entire screen glitched, which has never happened before. Logged in again to PC and League, it took me straight to the loading screen and then game within seconds.