Did you ever resolve this issue?
My TV has a similar Black stripe about 3" wide down the middle of the screen
It goes away after about 1/2 hour now (gradullay getting longer - was 5 mins)
Took it in for repair - guy thought it was a connector on the Graphics card - got it back was OK for about an hour then exactly the same.
Guy now says it might be the graphics driver card - sounds expensive!