"Garbled" postgres logs

While going through some log files, we noticed that some of the log entries
are "garbled". For example:

2007-03-27 01:19:44.139 UTC [1761474] oxrsa aepp xx.xx.xx.xx LOG:
duratio2007-03-n: 3751.27 01:19801 ms :44.139 statemenUTC [421940]
oxrt: EXECUsor
g aTE <unnaepp 10.4med> [P0.136.10REPARE: 8 LOG: select
durationname fro: 3866.1m epp_do88 ms smain_dz_tatementnames wh:
EXECUTere nameE <unnam = $1]
2007-03-27 01:19:49.213 UTC [528480] oxrsa aepp xx.xx.xx.xx LOG:
duration: 4510.129 ms statement: EXECUTE <unnam2007-03-ed> [PR27
01:19EPARE: :49
.213 select nUTC [294ame from930] oxr b_domsa aain_dz_nb
10.4ames whe0.136.10re name 7 LOG: = $1]

Here are the logging sections in the postgresql.conf file:

log_destination = 'stderr'
redirect_stderr = on
log_directory = '/opt/rg/logs/pgsql81'
log_filename = 'postgresql-%Y-%m-%d_%H%M%S.log'
log_truncate_on_rotation = off
log_rotation_age = 1440
log_rotation_size = 10240
log_line_prefix = '%m [%p] %d %u %h ' # Special values:

We're seeing this in postgresql 8.1.8 on AIX 5.3. Also, even though we're
using the same binaries for a bunch of clusters, we've only seen this issue
on one of them.

Any ideas of what could cause this?

--
Tim Goodaire 416-673-4126 tgoodair(at)ca(dot)afilias(dot)info
Database Team Lead, Afilias Canada Corp.