Error from pg_dump

  Yesterday, when our nightly database backup was running, it errored out
with the following error from pg_dumpall:

dumpSequence(contact_seq): different sequence name returned by SELECT:
contact_sequence


  Now, there isn't a sequence called "contact_sequence".  There's one called
"contact_seq", and the contact table references it like this:

    Attribute    |     Type     |                   Modifier
-----------------+--------------+------------------------------------------
 contact_id      | integer      | not null default
nextval('contact_seq'::text)


  What exactly does this error mean, and how I can track down what is
causing it?

steve