pg_dump and errors

Hello

Im getting strange errors when restoring data from pg_dump files:

ERROR: duplicate key violates unique constraint "products_pkey"
CONTEXT: COPY products, line 1: "98 Super Pak Ruby játék J-0001 1502450E Szuper Pokémon ajándékcso..."
ERROR: duplicate key violates unique constraint "attributes_pkey"
CONTEXT: COPY attributes, line 1: "2 Width"
ERROR: duplicate key violates unique constraint "prod_attributes_pkey"
CONTEXT: COPY prod_attributes, line 1: "1038 23 12 "
ERROR: duplicate key violates unique constraint "prod_images_pkey"
CONTEXT: COPY prod_images, line 1: "73 14 \\377\\330\\377\\340\\000\\020JFIF\\000\\001\\001\\001\\000H\\000H\\000\\000\\377\\333\\000C\\..."
ERROR: duplicate key violates unique constraint "manufacturer_images_pkey"
CONTEXT: COPY manufacturer_images, line 1: "296 81 \\377\\330\\377\\340\\000\\020JFIF\\000\\001\\001\\001\\000H\\000H\\000\\000\\377\\376\\000&F..."

Im using pg 7.4.1 on woody ( debian ).
this is not the first time such hapens and i have a constant fear from backup failures.

once I even had to move a db from 7.3 to 7.4 and pg_dump returned me some errors on not existing tables ( ones which i deleted before )

this is the line i use ( i started to seperate the scheme from the data becouse its easier to me to edit the files if something happens )

/usr/bin/pg_dump -s -f /var/pg_dumps/db1 db1
/usr/bin/pg_dump -a -f /var/pg_dumps/db1 db1

Any ideas how to avoid such errors ( if possible at all ) ?

Thanks
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