When I'm playing League of Legends, my monitor somtimes randomly says no signal?

Ok, so the launcher for LoL works perfectly fine, and in every other game, everything is fine. I'll be playing for a bit and then my screen goes black and says 'no signal', I can't hear the sound, but my box is still on, I've tried lowering my resolution, and there is nothing wrong with the cables, LoL has been working perfectly fine for 2 months prior to this, but it is becoming very annoying. My mouse and keyboard are light - up and they go off as well. Any fixes? My graphics drivers are up - to - date, and so is my DirectX, I've tried re installing, but still no bingo.