Missing database entry in pg_database

Hi,

I have a problem with a database i'm maintaining. I first noticed the
problem because i could not make a backup of the database i got the
following error:

pg_dump: missing pg_database entry for database "xxx"

I verified this by selecting the pg_database. It was indeed gone.

I did some more diggin and noticed that on doing a describe (\d <table>)
of a table i could not see any or some of the columns in the table, and
a few tables i also could just see the correct layout. It looks random.

The database is a very active database. It is running on Postgresql 7.3.
The database is getting a VACUUM FULL ANALYZE every night. No updates
where made on the machine and the error did not accour after a human
action as far as i can see.

Can someone tell me what happened here?
Can i fix my system table?
Can i still trust the other databases on the system?

--
"You can't reach second base, and keep your foot on first."

Groeten,
Robert