I had the exact same problem, we were watching the tv, and lines started appearing, and then what appeared like a crack. Samsung repair tech came out and stated that the tv was physically damaged. There is no damage to the outside of the sreen, tv was never hit, or dropped. It is in perfetly good shape and was purchaed in 1/10 and sill under warranty. Tech advised me that damage was our fault, and would not be covered under warranty. I took many photos of tv and emailed them to samsung, as it is quite obvious to me, and my husband who is an electrical engineer, that he damage is to the internal lcd board and that is where the crack is occurring. I was told I would here a reply in 2 business days. If you have any advice please let me know, as this was a perfectly fine tv, with no physcal defects, and it is quite apparent that the damage is internal. You can see when the tv is not on, there is not one crack or scatch on the screen.
I've had a Samsung LN52A since Feb. of 2009. The TV has been great up until last week when a crack appeared on the inside of the screen. It lso has what appears to be an impact point but nothing hit the screen and there is no damage on the inside of the screen. It is still under warranty so I called, repair ticket 4006118722. The tech didn't call for almost a week and then had my wife take a picture with a phone and send to o him. His response was that the screen had been hit. He came out and said the same thing telling my wife that someone had to have hit the screen. Trouble is my wife and son were watching it when it happened. HELP.