Updating a Sales Order Line using OData web services

Hi,

I would like to update individual sales order lines by using the OData web services. I can successfully retrieve said sales order lines from the following url:

(path-to-odata-web-service)/SalesOrder/(Document_Type='Order',No='some-sales-order-id')/SalesOrderSalesLines

but when I try to issue a PUT request to this url I get the following error:

"'PUT' requests for 'SalesOrderSalesLines' of EdmType 'Collection' are not allowed within Microsoft Dynamics NAV OData web services."

I've already included the correct "If-Match" ETag header in the request.

Any ideas?

Regards,

Daníel