WARNING: pgstat wait timeout

Hi all!

First of all thank you for this awesome database! We are successfully using
PG on top of Linux
in our projects for 2 years so far and are very happy with the performance
and observability
features of the database.

Recently we deployed PG 9.0.5-x64 on Windows Server 2008 R2 and noticed
very strange behavior:
at some time after firing up the DB it starts logging many 'pgstat wait
timeout' messages.
We monitor the IO, and it never goes higher than 10MB/s, whereas the total
throughput of DB disks is ~200MB/s.
I wouldn't bother, but the performance degrades soon after the message
starts showing up.

After some digging around I found that the reason is that
$PGDATA/pg_stat_tmp/pgstat.stat stops updating.
The workaround for me was to SIGHUP the DB -- pgstat.stat starts updating
and the warning stops.
Is this expected behavior?

If this is a bug what information will be helpful in this particular
situation to include in the bug-report?

Thanks!

--
Tair Sabirgaliev