Error Adding SalesOrder using SDK 6v5

In SDK 6v2 adding a salesorder works fine.

Doing the same unter 6v5 produces an error message:

"Update quantity in purchase order?[RDR1.Quantity][line: 2]

Does anyone have an idea whats going wrong ?

This are the lines of Code I use to add an order:

Dim sap_so As SAPbobsCOM.Documents

Set sap_so = sbo_cx.GetBusinessObject(Object:=oOrders)

With sap_so

.DocDueDate = VBA.Date

.CardCode = "C00001"

With .Lines

.ItemCode = "SP-2010.082"

.Quantity = 10

.ShipDate = VBA.Date

.WarehouseCode = "01"

.Price = 50

.Add

End With

.DocTotal =10

lReturnCode = .Add

End With