I have a new Premiere 4, and it seems to be having this issue. I'm almost certainly going to exchange it within a few days (I'm still within the 7 day initial guide data period).
It has HUNG several times with a frozen picture, when I come back to it. It *seemed* to be on HD channels at least twice. (Once I had put it in standby beforehand so I couldn't even see what was on the screen.) I turned off most of my HD channels as an experiment (on my Tivo HD, I have most HD channels turned off so that auto recording wishlists don't accidentally grab an HD show, wiping out tons of my recordings)
Last night, I had a recording going from 7:00 to 8:01.. and promptly at 8:00, when two new recordings were about to start, it rebooted. That lead me to think that it was hanging/crashing at "start a new recording" time. Only once have I had a partial recording due to reboot/hang in the middle of a recording.
The strange thing is, this *seems* different than other issues that would be caused by a bad hard drive. I *thought* I saw bad pixellation in one recording, but I happened to also be recording it on my TivoHD.. and I saw pixellation at the same spot (slightly different video effect, but the same spot) in both recordings.
So I'm paranoid that a replacement will do the same thing… But I still think I'll exchange it on my day off in a few days. (Obviously I have 90 days to exchange in warranty, so I'm not absolutely rushing back, but I won't pay to subscribe this one that seems like a dud.)