pg_restore and the missing blobs (oids)

Hello,

I have two servers running postgres 7.3 (Server Jupiter), and 7.4.3 (Sever
Saturn), in my office. I have a master database in Jupiter, that contains
a DB with images, OIDs (lo type).

I'm trying to backup the database from Jupiter and restore it in Saturn.

I do this, from Saturno:

pg_dump -Ft -b -U dbuser -h saturn dbsample > db.tar

Then, I create the user and database in Saturno, and perform this:

pg_restore -Ft -v db.tar -d dbsample -U dbuser

But, pg_restore stops, showing this message:

pg_restore: no OID type columns in table photos1
pg_restore: fixing up large-object cross-reference for "inventory"
pg_restore: no OID type columns in table inventory
pg_restore: fixing up large-object cross-reference for "photos2"
pg_restore: fixing large object cross-references for photos2.photo
pg_restore: fixing up large-object cross-reference for "parts"
pg_restore: fixing large object cross-references for parts.qltymemdoc
pg_restore: [archiver (db)] error while updating column "qltymemdoc" of
table "parts": ERROR:  large object 609937 does not exist
pg_restore: *** aborted because of error

But this large object, exists. I "untar" the "db.tar" file, and thereis
a file called "blob_609937.dat", and it appears in the file "blobs.toc".

Where is the problem ?
How can I do a safety reliable backup in postgres, with databases that contains
"lo" columns ?

I have tried with diferents options (dumping and restoring), but always
appear the same problem. This have seen this problem in databases using
large objects (lo type), since version 7.3.