Integrity Error

hello guys,
i am using openerp which uses postgres as its database .when i do some
database changes in openerp i get this error which is a reflection of
postgres internall error.do u have any idea what does it mean?
Error: "document_directory_group_rel" violates foreign key constraint
"document_directory_group_rel_item_id_fkey"
DETAIL: Key (item_id)=(230) is not present in table "document_directory".

i know that foreign key contraint avoid entering invalid data into a table
but how can i find this key and delete it?

thanks