ERROR: Could not access status of transaction ####

I'm using 7.4 in preparation for an overdue upgrade.
Yesterday I posted 2 questions that were ignored, so I'll try a third
now.

When doing a query I get same error as below, which are the results
of vacuumdb.

vacuumdb: vacuuming of database "airburst" failed: ERROR: could not
access status of transaction 7564911
DETAIL: could not open file "/var/lib/postgresql/7.4/main/pg_clog/
0007": No such file or directory

I'm only querying from 1 table.
I could really use some help.

----

Regarding yesterday's Qs, how best to un-import from pg_dumpall's
results?
I'd dump-all'd into a text file and imported it via a psql -f filename.
It had encoding errors AND did NOT make the database I needed.
Everything went into db postgres.

Please help.

Ralph Smith
smithrn(at)u(dot)washington(dot)edu
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