Have you forwarded your CA the article I linked, and clearly stated the purposes of the cert you're trying to create? It sounds to me as if they have not granted your cert the signing capability, and nor would I expect them to do so.
I would actually be quite surprised if your (or any) Trusted CA would agree to create the kind of cert required to act as the organisation cert, as it's a big risk (and costs a huge amount.)
What is your rationale for the replacement Org Cert?