pg_dump or hardware?

Hi all,

short summary:

platform: i386 SMP (dual PIII)
os: linux 2.6.8.1
vendor: debian (3.1, stable)
pgsql ver: 7.4.7 (deb)
disk: tech. SCSI vendor. IBM model. DDYS-T36950N rev. S96H
controller: adaptec aic-7892a

description:

we're experiencing a weird problem
trying to get a dump of our db for backup purposes,
the executed command is:

/usr/bin/pg_dump -U postgres -h 6pali elenco | /usr/bin/bzip2 > elenco_test.bz2

the output:

pg_dump: ERROR: could not open relation with OID 201327173
pg_dump: SQL command to dump the contents of table "nominativi" failed: PQendcopy() failed.
pg_dump: Error message from server: ERROR: could not open relation with OID 201327173
pg_dump: The command was: COPY public.nominativi (nome_cogno, indirizzo, cap, citta, prov,
prefisso, telefono1, telefono2, note, idpersona, estrazione, num_estra, occupato,
cod_prov, cod_com, cod_reg, capoluo, rand) TO stdout;

so it seems that we've got some problems with the "nominativi" table
(a 20 million-row table), in fact the following command also fails:

pg_dump -t nominativi -U postgres -h 6pali elenco | /usr/bin/bzip2 > nominativi.bz2

with the same err msg as before. Before the erros occurs we're are able to
get a partial backup, see:

#> ls -l nominativi.bz2
-rw-r--r-- 1 sickpig users 2.5M apr 19 12:35 nominativi.bz2

#> wc -l nominativi
145904 nominativi

We're trying to understand whether this is due to data corruption or
hardware failure. We run long self-tests on our SCSI disk through
smartmontools on a regular basis. see attached file for "smartctl -a /dev/sda"
output. All suggestions are welcome.

Regards,

Andrea