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, JVC TV's usually only have this listed as CC and it has an auto on - off selection. However if you don't 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.