AppleJuice,
It may be that the panel is fine, but one of the internal parts may be malfunctioning. I would recommend having the unit serviced and inspected.
--HDTech
My old 42" Samsung Plasma TV just got a pixel problem ( I think ).
I using it to play my playstation 3 when suddenly 2 bars of dead pixel appeared ( I think they're dead pixels, they're colored differently depending on the background). The 2 horizontal bars are located on the top and in the middle of the screen, and are about 3.5 inches wide.
Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic