I have a glitch/bug that i hope you can fix riot.

So, every time i play league Of Legends when the game is over and the camera starts to pan to the nexus, it suddenly freezes and i can't do anything, i cant even turn off my computer! as a result i have to constantly unplug my PC from the wall to fix it. so is there a way to fix this or do i have to just live with it? (I use a HP computer on windows 8 if that matters)