SQL0338 Error received on query

I have an application executing this query that used to work in iSeries O/S V5R4, but no longer works in V7R1.  I understand IBM made a change to the way they handle joins in versions 6.1 and above, but can't figure out a way to get around the error.  Here is the query:

Select H.PONumber, H.CreationDate, H.BuyerID, H.VendorID,
            H.LDC, V.DBVen_Vendor_VName, Coalesce(DBVLo_Addr1,
            DBVen_Addr1) as DBVen_Addr1, Coalesce(DBVLo_Addr2,
            DBVen_Addr2) as DBVen_Addr2, Coalesce(DBVLo_Addr3,
            DBVen_Addr3) as DBVen_Addr3, Coalesce(DBVLo_Addr4,
            DBVen_Addr4) as DBVen_Addr4, Coalesce(DBVLo_City_Addr5,
            DBVen_City_Addr5) as DBVen_City_Addr5,
            Coalesce(DBVLo_State_Prov, DBVen_State_Prov) as
            DBVen_State_Prov, Coalesce(DBVLo_Postal_Code,
            DBVen_Postal_Code) as DBVen_Postal_Code, S.StatusDescription
            From PMFPOHeader H, PMFPODetails D, PMFPORevision R,
            PMFPOStatus S, DBAPVEN V Left Outer Join DBAPVLo VL On
            VL.DBVLo_Vendor = V.DBVEN_VENDOR and VL.DBVLo_Location_Code
            = H.VendorLocationCode Where H.PONumber = 1000 and D.PONumber
            = 1000 and H.VendorID = V.DBVEN_VENDOR and S.StatusID =
            H.Status Group By H.PONumber, H.CreationDate, H.BuyerID,
            H.VendorID, H.LDC, V.DBVEN_VENDOR_VNAME, VL.DBVLo_ADDR1,
            VL.DBVLo_ADDR2, VL.DBVLo_ADDR3, VL.DBVLo_Addr4,
            VL.DBVLo_City_Addr5, VL.DBVLo_State_Prov,
            VL.DBVLo_Postal_Code, DBVen_ADDR1, DBVen_ADDR2, DBVen_ADDR3,
            DBVen_Addr4, DBVen_City_Addr5, DBVen_State_Prov,
            DBVen_Postal_Code, S.StatusDescription

Ideas?