unstable postgres on freebsd

Hi,

I seem to have an unstable/unreliable installation of postgresql, and I'm not sure how to troubleshoot it.

Symptoms:
$ psql postgres
psql: FATAL:  semctl(851974, 3, SETVAL, 0) failed: Invalid argument

(restart postgresql)
$ psql postgres
Welcome to psql 8.1.4, the PostgreSQL interactive terminal.
(rest of welcome message and psql prompt)

It will work fine for a while, but later it will stop accepting connections with the above error, until I restart postgresql again. It also happens when I call a ruby script that connects to postgres: fails with same error message sometimes, but works after restarting postgresql.

Versions/Environment:
Postgresql 8.1.4 (installed from ports on FreeBSD 6.1)

I've already tried reinstalling the postgresql81-server and postgresql81-client ports and their dependencies via portupgrade, but the symptoms persist. What else should I try?

--
Wes Sheldahl
wes.sheldahl@gmail.com