I had the same problem within 30 days of purchase. Returned the set for a new one. Now four months later the secont set has the same problem!
Had tv 3yrs. About a month ago, the at various times the tv screen would go blank even though the tv was still on and the lamp was still on. I cut off the tv and the picture would come back. It may stay for hrs or mins before the screen goes blank. I replaced the lamp. Problem continues. I called Samsung they recommended a tv repair tech near my home. He came out, checked the cable, video hook ups check the lamp and said he tightened the connections, etc. Problem continues. They sent someone else out and since the screen stayed on he advised me to call him when it happens and confirm the lamp stays on as well as the sound. He know thinks it could be a lamp engine. he other tech mentioned lamp cover. Once problem starts it becomes more frequent the longer tv is on.