Records deleting themselves...

Greetings,

I'm running pg-6.5.1 (upgrading to 6.5.2 as I write this) on
FreeBSD-3.1-release and I have an application that I wrote that uses pg on
the backend. Lately users started complaining about not being able to
login and when I would do a search for the account it was gone. There is
only one way to delete a user and that is from the psql monitor, and I am
the only one who has access to psql.

I do a vacuum and vacuum analyze from cron every night, as well as some
other basic clean-up sql commands, but none of them involve the users table.

Any insight as to why these user records are being deleted would be greatly
appreciated. Also, there does not seem to be any consistency on the deletions.

Thanks,
Matthew