Data corruption zero a file - help!!

Hi all,

I posted this on the novice mailing list and as yet had no response,
hopefully someone here can help.

While we where trying to do a vacuum / pg_dump we encountered the
following error:

postgres(at)db:~$ pg_dumpall -d > dump.pg
pg_dump: dumpClasses(): SQL command failed
pg_dump: Error message from server: ERROR: invalid page header in block
9022921 of relation "gap"
pg_dump: The command was: FETCH 100 FROM _pg_dump_cursor
pg_dumpall: pg_dump failed on database "monashprotein", exiting

Now after doing some searches I managed to work out that the data
corruption starts at 902292.137
using this sql:
SELECT * FROM gap WHERE ctid = '(902292,$x)'
Where $x I changed from 1-150.

as mentioned on this
post:http://archives.postgresql.org/pgsql-general/2005-11/msg01148.php

Following this post it seems all we need to do is re-zero from this
point on. However we're not sure which file to do this in.

I've worked out the database/relation files are
$PGDATA/37958/111685332.* with the max * being 101.

Any help locating which file we need to do the re-zero thing would be
really appreciated.

Cheers
Noel