This exact same problem just happened on my LCD two days ago. Below is my experience with the issue which I am posting on every forum i can find on the Internet.
I purchased my $4500 LN55A950 in Oct 2008 and has worked flawlessly until 2 days ago. The TV now has thin grayish horizontal lines going from right side of screen to the left diminishing in intensity until they fade out completely about 2/3rds of the way across the screen. The lines are about 1/4" apart and are present from the top of the screen all the way to the bottom of the screen. Plus the picture quality has gotten worse overall.
A Samsung-certifiedTV tech just left my house and said the LCD panel is bad and needs to be replaced. The replacement cost is $1800 with labor. The TV is 2 months shy of being 4 years old and obviously out of warranty. The tech said I would be an idiot to spend that kind of money to fix it when i could purchase a new one for about the same price. He then suggested i call Samsung and ask for relief as he has seen many instances where Samsung has provided help to customers with out-of-warranty repairs by shipping the part free with the customer paying for the labor. So I called, the agent opened a service request for me, then transfered me to customer relations. After explaining the problem once again and politely asked for relief as the panel should have lasted much longer that this, I was flatly told NO and that i had to pay the full cost for the panel replacement. I asked the person to please escalate my ticket for special consideration to OOP and again was flatly told NO, that she would not. "Company policy is clear in these matters". I am just flabbergasted that my TV requires a repair that costs nearly half what i paid for it in less than 4 years.
I know Samsung has been ordered to write a $1B check to Apple for alleged willing and deliberate theft of Apple-protected IP, but still this is just outragous. I have a Samsung dishwasher, refrigerator, washer, dryer, blueray player, and two smartphones. They have lost me as a customer for life as I cannot expect their products to last longer than they should. I am going to tell everyone I know about my experience and blog it where ever I can. If you are considering a Samsung purchase, think again.