[mythtv-users] What might cause a recording to mysteriously stop?

[f-myth-users at media.mit.edu]

I just noticed something odd.  I'm running 0.18.1 (yes, 18) with
verbose logging on the master backend and several PVR-250's in that
backend using ivtv 0.4.1.  (There's also a separate frontend that also
has a slave backend in it, but that machine wasn't recording, and in
fact wasn't even in use 'cause I wasn't even here at the time.)

Several recordings were in progress simultaneously, including one that
was supposed to run from 8-9pm with one minute of padding on each
side.  That one recording only recorded 47 minutes and quit.  All the
others recording at that time are fine.  They're all using the same
signal source (RF directly from the cable feed).  Mythweb still claims
it's a 1h2m recording, but it's several hundred meg too short, and
playing it back on the frontend also claims it's only 47m and it
indeed quits at that point.  (I noticed this at all because the actual
.nuv file in the directory was last modified at 21:47, which jumped
out at me as a peculiar end-time for anything on that channel, which
always schedules by the half-hour or hour.)

There's nothing at all in the backend log; in fact, there aren't any
entries at all for at least 10 minutes on each side of that time.
None of the other logs in /var/log that I've looked at (syslog,
messages) have any entries for at least a few minutes on each side.
The recordings directory (JFS) has about a hundred gig free.  This
setup has been stable for months and nothing's been changed recently.
The case doesn't run hot and I've never noticed any power supply
issues.  The database was last checked and optimized maybe 12 hours
before (not that I would expect a DB issue to stop ivtv).

Ideas?