Schema-instance:type' attribute must be specified for every parameter

[Da...@kp.org]

My web service client report the following error:

exception: [SOAPException: faultCode=SOAP-ENV:Client; msg=The 
'http://www.w3.org/1999/XMLSchema-instance:type' attribute must be 
specified for every parameter.None was specified for return; 
targetException=java.lang.IllegalArgumentException: The 
'http://www.w3.org/1999/XMLSchema-instance:type' attribute must be 
specified for every parameter.None was specified for return] 

Looking at the actual data going over the wire and coming back I note 
several thing:
1) The server successfully executes and returns the correct data. So this 
error occurs
client side, while processing the response.

2) The return type is specified in the return envelope as can be seen 
here:
<return xmlns:ns2="http://www.adapter.com/schemas/AdapterRemoteInterface" 
xsi:type="ns2:org.member.ws.SearchResult">

3) The outgoing envelope has the "xsi" and "xsd" namespaces set as:
xmlns:xsi="http://www.w3.org/1999/XMLSchema-instance" 
xmlns:xsd="http://www.w3.org/1999/XMLSchema"

But these namespaces on the return envelope are 2001 XMLSchema:
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
xmlns:xsd="http://www.w3.org/2001/XMLSchema">

So the client is generating types using the 1999 XML schema, and the 
server is generating 2001 XML
schema types. Is this mismatch of  XMLSchema types the cause of this 
error?

Thanks,
David