That TV is 4:3 shaped, no? Cos I get the same thing on my 27" SDTV when I apply the "anamorphic squeeze". But if I set the TV's picture mode to "Movie" -- which, among other things, darkens the picture a bit -- that lighter shaded bar becomes darker, very very close to the black of the black bar produced by the anamorphic squeeze. Give that a try: lower the brightness of the picture, and you may find that the two bars more closely match.
cheers,
supervij