I have two HR20s and have only been a customer a month now. One was already replaced due to a bad tuner #2, and one was replaced do to problems like what you described, but with no rhyme or reason, just several random lockups and reboots.
They replaced both with a little work, I had to be very stern as to wanting a replacement, not a tech, etc. Of course they wanted to switch the switch/lnb first, I said forget that, the other receivers work great. They will due it, keep going up the ladder to the next level.
Anyway, after getting both replaced I called retention just venting as to the problems and my down time, and received a $50 service credit and a $100 hardware credit. The hardware credit was to bring my second HR20 to the $199 price. Now I have to wait and see if I get the $100 mail in rebate too...
I think in my first two weeks, I spent 5+ hours on the phone with them.
No problems the past two weeks, except one unit will lose the signal on 103 sat, local HDs. I ended up unplugging all receivers for 15 minutes to reset the switch (did this myself, not sure if it works like that or not) and the problem has not reappeared.