Big Black Box appears in the Middle of the TV screen

I just got a new H20. Every once in awhile a Big Black Box appears in the Middle of my TV screen. It randomly does this about 2-3 times an hour. It seems to hapen when I change channels or menus? I Called D* Technical Service and they where no help. I spent over an hour with them and they had me do the usual stuff, reset, unplug, ect... The Tech said that she had never heard of this and did not know what to do about it? The only way I can make the Black Box temporarely disappear is either (to turn it off/on) or I can (Reset the receiver) or (on a few occasions just change to another screen and it will go away).

I know it is not my TV, because I can switch over to Cable TV on the same TV and not experience any problems.

Any suggestions would be appreciated. I'm just about to pitch the H20 out in the street!

Thanks!!!