While playing City of Heroes my screen suddenly went black and I was unable to do anything in that state so I shut down my computer and tried to boot it back up. For several minutes I was unable to even turn on my computer as in no power up noise, no lights turning on nothing. I checked all my connections outside of the computer and everything was fine. Then a few minutes later I was just suddenly able to turn the computer on again. What is the likely cause of this problem? If you need any more specifics feel free to ask and I will provide.