The black square / box is associated with the text function on the TV even
although the TV might not be receiving it, and this is a procedure that gets
over the problem on "some" chassis.
If you have a "closed caption" button on your TV's remote control press it
until the black square disappears.
However if you dont have that button on your remote control try this /
Bring up the menu and highlight "closed caption", to access this menu press
the "volume +" button.
When you enter this menu it will say "mode text"
Press the "volume +" button until it says "mode off", then press the
"channel -" (minus) button and highlight "finish".
Finally press the "volume +" button to save your settings.