Vacuum command

I've had trouble in the past with the vacuum command taking a long time
to complete. This past vacuum went for 5 days before I CTRL-C'd it. I'm
wondering if there is a bug.

I have PostgreSQL 6.3.2 on a Red Hat 5.1 system (PII/400 MHz, 256 Meg
RAM, 512 Meg Swap, 18 Gig Hard Ultra-wide SCSI Drive). The database
consists of about 30 tables and is 1.2 Gig in total size.

When I ran 'vacuum verbose analyze' the last time, the vacuum kept
working for 5 days until I killed it. I had no other programs running on
the system at the time. Also, I noticed that although 'top' showed that
the vacuum was using 98% of the system resources, the harddrive activity
was quiet during that 5 day period (as if nothing was actually
happening).

However, I then tried 'vacuum verbose analyze table_name' to vacuum just
one table at a time. When I did it one table at a time, I was able to
vacuum all 30 tables in less than 1 day.

I know that others have had there run in with long vacuums. I am
wondering whether there is a bug when the vacuum switches from one table
to the next?

-Tony