I had an HD dish and 722k installed two years ago. Never a problem until the last week to 10 days, During that time I have had several occasions when I enter a channel number, the receiver switches to it and shows the Complete Signal Loss screen. Almost every time, I do a channel down and a channel back up and the channel displays properly. On one maybe two occasions, I got repeated Signal Loss after doing channel down, channel up several times. I switched to another channel and then a few minutes later when I went back to the originally requested channel and it displayed properly. Rebooted the receiver today and already saw the Signal Loss screen once. Any explanation.