FATAL 1: Relation 'pg_shadow' does not exist - Mailing list pgsql-hackers

I am getting this error when I attempt to connect to a production
database. All other databases have valid pg_shadow and appear to be fine.

The database version is
PostgreSQL 7.1 on i686-pc-linux-gnu, compiled by GCC egcs-2.91.66

Logging was going to the terminal (completely useless, I know) but there
was an interesting error from a VACUUM of another database on the system:

NOTICE:  Rel qafinal_fti_i: TID 2023/112: OID IS INVALID. TUPGONE 0.

The affected database was not being vacuumed, not had it been since I'd
seen it 'stable'.

Does anyone have any ideas about this? Anything to prevent my needing to
go to tape and spend a long night in a cold cold server room?

Thanks

Gavin