I have an XMLAPI Insert Error problem

I have an XMLAPI problem that I am unable to resolve.  I am trying to insert two Billing Line items for a unit price billing one is a req_detail_type 1 ("Unit Price") and the second is the companion record for req_detail_type 5 ("Unit Price").  I am able able to insert one or the other req_detail_type records but as soon as I try to insert the second record I receive the following error:  - This shows both the successful insert for RequisitionLine Item Number: 0000003 for req_detail_type 1 and the failed insert for RequisitionLine Item Number: 0000003 for req_detail_type 5.  I