Problem with Creating Cash Sale - Webservices

Hello-
Am using WSDL 2.6, having trouble creating a cash sale.  Here is the error returned:

[Error]: cash sale failed 32 - [Code=INSUFFICIENT_PERMISSION] You do not have permissions to set a value for element createdfrom due to one of the following reasons: 1) The field is read-only; 2) An associated feature is disabled; 3) The field is available either when a record is created or updated, but not in both cases.

This is the code - basically the sales order is passed into the function (SalesOrder so).

 private void generateCashSale(SalesOrder so)          {              CashSale cs = new CashSale();              // create and reference original sales order              RecordRef soRecordRef = new RecordRef();              soRecordRef.internalId = so.internalId;              soRecordRef.type = RecordType.salesOrder;              soRecordRef.typeSpecified = true;              cs.createdFrom = soRecordRef;                // create and reference the customer record              RecordRef soEntity = new RecordRef();              soEntity.internalId = so.entity.internalId;              soEntity.type = RecordType.customer;              soEntity.typeSpecified = true;              cs.entity = soEntity;                           // Note: we may need to manage the ccApproved member here - as noted by NS              cs.chargeIt = true;              cs.chargeItSpecified = true;              WriteResponse res = _Service.add(cs);              if (res.status.isSuccess)              {                  _Out.writeLn("cash sale created " + so.tranId);                  updateSalesOrderExportStatus(so, "4");              }              else              {                  _Out.error("cash