Monitor Blacks Out When Game Opens

I've done some digging around, but I can't seem to fix the problem. It's happened 3 times on separate occasions and only with league. Everything will be fine, but at the end of a countdown in champ select, my screen will go black just as the PVP client should open.

The light on my monitor goes orange. Turning it on and off does nothing. I have to reboot just to bring it back, which makes it hard to be punctual.

I don't think this is a hardware issue, cause I've played all kinds of other games in between. Just when I play league, RIGHT when the PVP should launch is when it happens. I only have the one monitor. No other display devices.