pg_dump: schema with OID 559701082 does not exist

Hi,

I get the following error when I call:

# pg_dump  db
pg_dump: schema with OID 559701082 does not exist

this happens with 8.0.1 on RHEL 3.0. I cannot dump the database neither
with --schema-only or --data-only.

What can I do?

Thanks for help,

Dirk