My 5500 doesn't do it when I turn the TV on game mode. I haven't tried any of the other modes, but I know when I first was using my 360 and didn't have it on game mode, it happened on all of the loading screens. With game mode on, it doesn't happen on any of the screens.
If you have a screen that is completely black except one small part, (i.e. an all black screen with the text "Loading" in the center), you don't see a band that goes across the entire set that makes that row lighter than the rest of the set?
Suppose the text "loading" is bright white.
"=" means dark
"0" means light
You really don't see this at all? What version of the tv software are you running? If you have a chance to post your settings, please do.