I Can't Complete a game!

I've recently gotten lol and a 25$ gift card for it, and so far it's been fun. It ran perfectly fine this morning and yesterday, I had zero troubles playing the game. However, in the last couple of hours I've gotten a really frustrating bug. I will be in the middle of a game when it will suddenly freeze, and I can't do anything. Literally anything. I can't even open my task manager to force the game to shut down, and ctrl alt delete doesn't work either. It's happened three times, and I've received a warning for it. Not cool.

The warning message says, "A Critical error has occurred and the process must be terminated. This is usually due to the result of incompatible third party software being installed on your machine. Please disable any overlay, streaming, or experience 'enhancement' software. Additionally, you may need to white list this application with your installed security software."

I don't have any overlays, I don't stream, and I'm not cheating. (That's what I assume that means.) This is getting a little frustrating, being among my first times playing the game. I've restarted my computer several times and I've gotten no fix. I am running nothing, literally nothing, in the background, so I have no clue as to what it could be meaning. Thanks!