Panasonic CT-31SF70R Picture Problem?

I've had a trouble-free Panasonic 31" flat screen for 11 years. Over the past few months, (right after turning the set on and then for several minutes after warm up) there have been stacked horizontal white lines showing up at the top of the picture. (mostly at the top 5-6 inches of the screen) The lines would eventually disappear or become not as noticeable after the set was warm. Today, I turned the set on, and I get perfect sound, and channel tuning, but only a single horizontal line through the center of the screen. There must be a picture, because I can see color changes in the line, and the back of the picture tube is lit up when the set is on, but functionally, the set is now useless because 99% of the screen is black and pictureless. This set has mainly a large picture tube, and a full component board. Any thoughts on wether its worth repairing would be appreciated. I'm thinking I may have been lucky with the trouble-free years I got and should move on since repairs may cost me more than a comparable new set. The picture was still great up until today, so I'm hesitant to put it out on the curb just yet. Any opinions would be appreciated.