[CRASH] Inescapable Black Screen Post Game

After finishing a game I will click the victory or defeat button and a black screen will come up. I do not have a cursor or anything else on the screen at all. it does not allow me to alt tab, escape, crtl alt delete or alt f4 out of this screen. However, things such as pandora and skype are still running perfectly normal in the background and functioning fine as I can still hear them.

This has happened on three occasions thus far and has not happened to my computer other than directly following a League game. So far it has happened only on summoner's rift, but has happened on both PvP and Co-OP v Bots.

It does not occur very often, I would maybe every 10 games or so and has occurred with different champions each time. The only way I can get rid of the black screen is through a hard reset. Obviously this is not good for my computer I would like to stop having to do this.