Discoverer report with PO_RELEASES in R12

Hi all,
I'm migrating a Discoverer report from 11i to R12. The query of the folder uses the po_releases and this join condition "and rcv_transactions.po_release_id = po_releases.po_release_id(+)". When I run the report I get the error "invalid number" but when I tried the same query but using the po_releases_all it seems to work. Is this ok? I saw that in R12 po_releases is just a synonym, is this correct? I would appreciate your comments.
Thanks in advance.

Thanks Hussein. Yes, I've checked the document you recomend, but the problem seems to be when I try to use po_releases, the synomy) and I don't know why it work with the _all table but not work with the synonym.