Update error in NetWeaver Gateway

Hi,

I have created a service in Gateway. I get the results when I use GET for my url.

http://xxx.sap.corp:1080/sap/opu/odata/sap/ZICP_SO_SRV/SOSet('0500000004')/SOItemSet(ItemPos='10',SOId='500000004')

When I try to update the content using PUT method from Gateway client, i get the below error.

<?xml version="1.0" encoding="utf-8" ?>

I am using the same url which is used in GET, this gives me the exact line item of sales order which needs to be updated.

I have also implemented Update methods in the generated class.

Can anyone help me here?

Thanks,

Swetha