Post game..

So after a game ends (when the scores and stuff are shown) recently instead of that my computer has been going automatically into sleep mode at the end instead of showing the score or going back to the lobby, and I can't leave it or even do anything expect manually turn it off by holding the power button off. I can't tell if it's just my computer overheating excatly when it ends or something wrong with my computer (which shouldn't be since I just got it a couple months ago and has had no virus or anything on it previously or detected) OR just something wrong with my client...
Can someone help me sort out at least where the source of the problem is?