I have a JVC AV-48WP30 and i recently have gotten a rectangle black band across the screen. cannot get it out.

the band is on when trying to view, when i change channels it disappears momentarily and reappears. the band is about 10" high and 32" across the screen . is it something that i can adjust through the menu or what help please. the band will also disappear when i use the freeze , split,or pop screens.