Help - corruption issue?

While doing a PG dump, I seem to have a problem:

ERROR: invalid memory alloc request size 4294967293

Upon googling, this seems to be a data corruption issue!

( Came about while doing performance tuning as being discussed on the
PG-PERFORMANCE list:
http://postgresql.1045698.n5.nabble.com/REINDEX-takes-half-a-day-and-still-not-complete-td4005943.html
)

One of the older messages suggests that I do "file level backup and
restore the data".
http://archives.postgresql.org/pgsql-admin/2008-05/msg00191.php

How does one do this -- should I copy the data folder? What are the
specific steps?

I'm on PG 8.2.9, CentOS 5, with 8GB of RAM. The disks are four SATAII
disks on RAID 1.

Thanks!