Can I fix my Toshiba 27"?

I have a standard Toshiba 27" TV (not sure of the model #)that is only 2 years old. We do run it a lot though. We started getting 3-4 thin parallel white lines that are almost horizontal along the top of the screen. They are noticeable but don't really interrupt the picture. Now today, after the TV had been off for awhile, I turned it on, and there were even more lines--from the top of the screen down about 4 inches. After the TV runs a bit, the lines get less and less until there are only 2 or 3 up towards the top. Any ideas? Can this be fixed easily/cheaply?

Shirley
March 2007