Table has 22 million records, but backup doesn't see them

Greetings!

I'm running PostgreSQL 8.1 under Windows XP, looking at a database hosted on a machine running PostgreSQL under Windows Server 2003.

The database has a table with three simple columns and 22 million rows.  I am trying to back up that table by itself.  However, pg_dump finishes almost instantly, obviously not backing up any data from the table.  I've tried it from the DOS command line with and without the -a (data only) option, and from inside PGAdmin.  Can anyone suggest what might cause this behavior?

I'm going to have to do a full database backup, which I've been trying to avoid because there are other large tables I don't need and don't want to waste time getting.  A full backup of this database takes something like three hours.

Thanks again!