Advancto SFDC CommunicationChannel Error

Hi gurus

I am working on SAP-PI-SFDC (synchronous) interface and i am using the Advancto SFDC communication channel.

I am using the message protocol as APEX WebService and the configuration usage as "Define explicitly". When i am trying to test the interafce i am getting the follwoing error in PI RWB.

Error: unable to find end tag at:  START_TAG seen ...INEITEMS>\n               \n               <aces:XXX_XXX_XXXXX>... @16:41 (Software version: 1.0.26)

I am not using any mapping; the wsdl is provided by the SFDC guys and i am using the wsdl in PI and the flow is Proxy(OB) to PI -SFDC.

i am unable to understand the error, require your help in overcoming the issue.

Thanks a lot in advance.