I have an HDVR2 running 6.3 that decided it had 2 tuners again about 2 weeks ago. I was getting ready to unplug it and trade out for another HDVR2 (zippered, and running 6.2, whose 2nd tuner doesn't pixellate). At some point during the process, where I was unhooking sat cables from one to get data downloaded on the other, the 6.3 one froze up. When I rebooted it, I think it decided it should have 2 tuners again. I didn't realize this for a day or so.
The 6.3 receiver is still running, since we had a few things we wanted to watch that were still on it. I've noticed it seems to freeze up more often than when it was plugged in (sat lines and phone). My wild unfounded guess is that attempts to call-in are somehow leading to the freezing.