I have seen vertical lines on LCD's, one or more pixels wide. These were swapped in a repair shop, so thought there was some ESD damage to the drivers on the LCD module. The lines were still there when the cables, controller were switched. The rest of the display still worked OK. It may have bad contacts to the LCD electrodes, as well, this could give the same effect, although open contacts may leave the addressed line "blank" not black. -Dave

http://www.netcomuk.co.uk/~wwl/Plasma.html