game breaking bug after champion select.

I try to play a ranked game not 5 minutes after I played the last one and instead of a loading screen, all I get is a black screen with a cursor. This has happened once before and I solved it by switching off my firewall, but this time that didn't work and now i have a ranked leave on my record. I don't want to risk making anymore 4v5 matches so I have been testing to see if the issue persists by trying to spectate games. the game remains unplayable and I still have not found a solution.