Database 'xxxx', OID yyyyy, has disappeared from pg_database

I receive the following error when trying to connect to ALL postgres
databases on my system.

Database 'xxxx', OID yyyyy, has disappeared from pg_database

The various archives have other users that had this problem and the
solution is to vacuum the pg_database, however;

bash$ vacuumdb pg_database
psql: FATAL 1: Database "pg_database" does not exist in the system catalog.
vacuumdb: vacuum failed

I also cannot connect to any database precluding me from running vacuum
pg_database from the psql command line. I cannot create a database and
attempt this as,

bash$ createdb tester
psql: FATAL 1: Database 'template1', OID 17216, has disappeared from
pg_database
createdb: database creation failed

Any suggestions?

RedHat
Linux Kernel 2.2.14-5
PostgreSQL 7.0.0 - yeah, I know I should have upgraded. SOL?

Thanks in advance.

--
Michael Glenn
http://www.mglenn.com
416.544.9904