This evening I received a new HD receiver for my bedroom. Up until today I had an SD receiver in the bedroom, an SD receiver in another room and an HD DVR in my living room. The person I spoke with said the new box should just need to be plugged in and it would work. It does, sort of. The SD channels are working just fine but when I go to any HD channel it tells me its searching for signal in Satellite 1 and gives me error code 771. I've already had to change some things because I was getting error code 771A and before then it wouldn't do anything, including load the guide. What is my problem and how can I remedy the situation?