Without being able to really offer a thorough diagnosis, it may seem to be electronics related rather than the actual panel itself with regards to the banding. Your technician would be able to address that more properly than I would be able to.
If the screen scores are staying up for just being displayed for a minute, it may be possible that your brightness/contrast settings are set too high, or are on "Dynamic". I would suggest seeing if turning down some of those settings would help.
I have had the PN50A650 Plasma for almost a year, and it has been flawless with a great picture. Recently I've noticed a horizontal band about 4" wide, in the middle of the screen that is slightly discolored. It's noticeable and a bit of a problem on light color backgrounds (ie: Winter olympic sports, hockey games, skiing, etc..) and doesn't depend at all on the input to the TV. Actually, it shows up even more on the "White" screen for burn in protection. Also, recently image retention has been absolutely horrible! Even after 1 minute of a sports score on the screen, the score is stil visible through the commercials.
I called 1-800-SAMSUNG and a repair tech came by, he's got to look into "something"... I'm waiting for his answer.... anyone else with these problems, or know a solution?
I'll post what I find out.