problem with psql?

We just ran an OS update on an Xserve which runs our PostgreSQL
server, and now it seems that pg_ctl status doesn't report the
correct status.

~ postgres$ pg_ctl status
pg_ctl: neither postmaster nor postgres running

~ postgres$ ps auxw | grep postgres
postgres   491   0.0 -0.1    33156   1160  ??  S     1:09PM
0:00.16 /usr/local/pgsql/bin/postmaster -D /Volumes/DBRAID/pgsql/data
postgres   629   0.0 -0.0    31844    216  ??  S     1:09PM   0:00.27
postgres: logger process
postgres   631   0.0 -0.0    33140    744  ??  S     1:09PM   0:00.06
postgres: writer process
postgres   632   0.0 -0.0    31860    276  ??  S     1:09PM   0:00.02
postgres: archiver process
postgres   633   0.0 -0.0    32864    164  ??  S     1:09PM   0:00.02
postgres: stats buffer process
postgres   634   0.0 -0.0    31888    284  ??  S     1:09PM   0:00.03
postgres: stats collector process


We are able to connect to the instance (using psql), but cannot shut
down or restart the instance using pg_ctl (it just reports that the
server is not running).  We are running PostgreSQL version 8.0.0 and
Mac OS X 10.3.9.  Can anyone tell us what's going on?

Thanks!
Tim