All I can think of from your description is that one of them is an LG Tv set. In that one you should try and find a way to turn off native resolution of the tv set. Please inform the make of the other Tv set, or both should I be wrong, so maybe someone else has a hint.
Also: Make sure both devices (tv and u1) are turned off before connecting the hdmi cable.
Normally your Tv set should have a path like this to follow regarding directtv: "menu/set-up/system set-up/HDTV/ and then turn Native Resolution "Off"