One solution ...

Hi, I have a Samsung PS51D555 which is about 7 weeks old and this thin line (top of the screen) problem came a few days ago. I sent an email to the local Samsung -service and they answered just a couple of hours later. A tech wrote that he will come to my house to check this problem (because all over 37" tv's belongs to the home service first). Well, a couple of days later he came (actually today) and took the back cover off. There was a connectors on the left side of the panel and he took every connectors off and pushed them back. After that, the power on and this thin line was disappeared. A whole thing took about twenty minutes. He told that this was a most common reason for this thin line issue. So, I can only thank this local service here in Finland!