Upgrading postgresql-8.4

I have a database that's about 600 GB. I did a pg_dump (pg_dump --format plain --create --encoding UTF8 --oids --verbose --file "/var/tmp/145_backup.sql" "digi") and, after 442 GB, I got an error, "pg_dump: Error message from server: ERROR: missing chunk number 0 for toast value 49209130 in pg_toast_17031". This was using postgresql-8.4.3 on Ubuntu 10.04. I upgraded our postgres to 8.4.16 using 'apt-get install postgresql-8.4'.

This went well and postgres restarted just fine. However, now when I execute a pg_dump I get a missing chunk 0 for pg_toast_2619 while querying pg_attribute. I did a reindex on pg_toast_2619, then tried to VACUUM ANALYZE pg_attribute but again got the missing chunk 0 error.

Did I miss a step doing the upgrade or recovery attempt, or is the data corrupted? I did the postgres upgrade and pg_dump on another server and it went very smooth so I'm flustered at how the problem seems to have gotten worse.