I have a Panasonic TX-28DT30 IDTV and have a problem with a vertical line on the screen. I know some other owners have the same problem, but I don't know the cause. I was wondering if the cause could be the same as yours, i.e. interference caused by the power supply.
The line is a thin dark band from top to bottom of the screen, always in the same position, about 40% across from the right hand side of the screen. It's not visible all the time--visibility depends on the picture. I only see it when watching digital TV, not analogue TV or an external source like DVD.
I also have a problem with a moving vertical line, scrolling from left to right across the screen at intervals of about a second. This does not appear when watching the TV signal directly, but affects the output to scart, so I see it when playing back a recording. Oddly, however, it only occurs if I am watching from the scart while recording. (I do this quite often, using the Timeslip feature of my DVD recorder.) This is definitely not crosstalk on the scart cable.
Any ideas what the cause could be?