Black box in middle of screen
Note that the large black box goes away when pushing buttons on the tv (ex: the black box will disappear to show the volume setting when changing the volume on the tv but it will cover the picture and the menu display of the dtv box).
This is caused by the closed caption setting of the television set NOT the captioning of the converter box. To fix this you must open your television's menu, find the ccd/closed caption option, and turn it off. This is a frustrating problem as when most people are told to shut off the captioning they try to do so at the box.
Normal dtv box captioning will appear as a small text box at the bottom of the screen as you would expect - not as a giant black rectangle that covers most of the screen. If you do want to shut this off too you will find that you can't do it through the usual menu options (the menu will only allow changes to font, color etc.) - there should be a ccd button on the remote that when pushed will scroll through ccd-1, ccd-2,... off.