My hr21-100 keeps freezing up. It started three days ago. I have another hr21-100 and an h21-100 and those are both working fine. I have whole home dvr and went to watch something in another room and noticed I couldn't see anything on the troubled box. I then went to the troubled box and it was unresponsive. I reset it and i thought that fixed it but over the last two nights the box keeps freezing up. Sometimes the screen will freeze and then start working again. Other times I get a signal strength error message (771 or 772 I believe). Sometimes even when the picture is not freezing I will get the error message. The times between freezes seems to be getting worse. All cables appear to be connected fully and nothing has been moved recently. Is there something I should do or is it the box? If its the box will directv replace with the same box or would it be an hr24? Thanks for any help. Merry Christmas.