For some odd reason, my system goes berserk when I try to watch something on 125W. The box simply stops responding to ANY commands, so I ultimately have to power cycle AND go to roof to reset the motor, because after that dish won't move automatically anymore (I can still drive it to reference manually, though). I've noticed that there were only C-band frequencies (4-digit) in the TP list, and I deleted all of those (this is a KU band only) and added the 12040 and 12179 freqs. manually, etc., and still does the same thing. I start watching, for example, PBS Montana, and then, when I try to change to another channel, it freezes. Anyone else having a similar experience?
My comments are relative to an 8100 not an 8000, but those two receivers are basically the same.
What you describe is interesting. My first 8100 worked nearly perfectly, but I lost it to lightning. My second one that replaced the first one, however had a defective fan, and it quickly overheated. It started doing what you describe within the first half hour I was using it. I noticed that it was overheating, and determined that the fan wasn't turning, so I put a computer fan on the top. This kept it cool, and it wouldn't freeze up for several hours, but it was still freezing. I sent the receiver back, but it came back with the same problem. I tried half a dozen different firmware versions, including both factory and a couple hacker versions. The firmware versions first changed the freezing behavior to a rebooting behavior, and later it seemed to allow me to run the thing for a couple days before it would reboot. The most recent factory firmware would only reboot once ever 2 or 3 days I think (I haven't used the receivers for over a year, since I replaced it with my Azbox).
Anyway, I found it interesting that you only had the problem on AMC21, since basically all I had programmed into the thing were the OTA ATSC channels and AMC21 PBS channels. I really can't imagine any reason why it should matter what sat you were on, but it's interesting enough that I have half a mind to resurect the 8100, and park it on some other sat for a while, to see if it still has the problem.
It's also interesting that in my case, the freezing symptoms changed from freezing to rebooting. Ie when it would normally freeze up, mine would now just reboot, and eventually come back to life, and since I left it on all the time, it would reboot when I wasn't watching, so I could sometimes go for a week without ever observing a reboot.
Anyway, I was convinced that the problem was caused by overheating, so you might try running with the cover off to see if that helps. I pulled the fan from my first dead 8100 and put it in the new one, but it isn't much of a fan, and I think most 8000s don't even have a fan.