My 722 died (4years old and very well behaved up until its death). Got an exchange unit. Installation seemed routine but it took a while for me to get 'normal' satellite reception. No problem with the Guide and the OTA reception. Well, now I get the satellite channels but not in HD. The satellite HD channels have a blank (black) screen. All the OTA channels are well received in HD. Is there one last tweak that someone can suggest?