I have had a problem similar to that twice now. First time my monitor would go out randomly and after unplugging and restarting everything it worked for a while. Only after a week did i find out my LCD monitor died after a short 6 months (must be because dropped it from about a foot). Second time my GPU was not getting power it needed all the time, found out my PSU was fading in and out. Would start on occasion then other times only what it could power would start. Not sure if it's the same time but could hurt to check with another PSU, unless you're sure it's not it.