pg_dump Backup on 7.0.3 - Sanity error?

I'm trying to use pg_dump to backup my tables one at a time from
Postgres 7.0.3 (I'll upgrade to 7.1 in a few weeks). I'm getting a
strange error that I've never encountered before.

The backup call is:    pg_dump db01 -t cell | gzip > cell.backup.gz

The error is :  failed sanity check, table ro_ellipse was not found

However, I wasn't even accessing table ro_ellipse. Plus, I've verified
that the table does exist and appears fine (I can select data from it).
I vacuumed the db and even restarted the postmaster, but I still get
this weird warning.

Anyone seen this before or know if this is a problem?

Thanks.
-Tony

Postgres 7.0.3 running on RH Linux 6.2 (Zoot), Pentium III/400 MHz, 512
Meg RAM