failed sanity check, table answers was not found

I receive this error when trying to pg_dump -s

    failed sanity check, table answers was not found

the failed table name varies. All the problematic tables
seem to work. vacuumdb (-z) also works without any comment.

This is a production database on 7.0.3
I'd like to migrate to 7.1, but I am affraid that the dumps are corrupt.

regards

--
Marek Pętlicki <marpet@buy.pl>