Picked up an AM-21 on Ebay. Installation on my HR54 was easy and straight forward. A couple of weeks ago I set up my antenna and used it by attaching it directly to my TV. The antenna pulls in all Boston market stations and most Providence market stations for me. (It's pointed at Boston.) It works great when connected directly to my TV. When I set up the AM-21 on my HR54, most of the stations I was getting with the direct connection were added to my DTV's guide. All was working fine - for about 2 hours. Then I started getting 'your signal is too weak' messages on a black screen on ALL OTA stations all at once. I thought it might be a bad USB cable (I was using the one they sent me), so I changed it with one I have that I know works for something else I have. I've since tried a third one, and even gone back to the original one - there is no difference in terms of the symptoms I'm getting with any of the cables. If I remove the USB cable from the HR54 (leaving both the HR54 and AM-21 on), and plug it back in, all the stations reappear like new. About an hour or two later, they go back out. It doesn't matter if I leave the HR54 on, or turn it off. (The AM-21 turns on and off with the HR54.) I've checked the OTA signal strength in the menu for that. Most stations are 85% and above, all are at least 60% and above. So, most stations are 'green' on the graph, some yellow. One thing that concerns me there, however, is tuner 1 - the signal strength is almost always much lower than it is on tuner 2. Sometimes tuner 2 will show 90%, and tuner 1 will show nothing. Sometimes both tuners will show the same signal strength. Because this is new to me, I don't know if this is normal or not. I've rebooted both the AM-21 and the HR54 a few times - it hasn't changed a thing. I also reset the AM-21 connection in the menu (went through setup again) - that did not work either. Thoughts?