Deserializer exception

Hello,
 
I am getting the following exception: No Deserializer found to deserialize a 'http://schemas.xmlsoap.org/soap/encoding/:string' using encoding style 'http://schemas.xmlsoap.org/soap/encoding/'
when running my source code.  I am using Axis 1.2 and Apache Soap 2-2
Can you suggest a solution?
 
Call call = new Call();
call.setTargetObjectURI(urn);
call.setMethodName(methodname);
call.setEncodingStyleURI(Constants.NS_URI_SOAP_ENC);
Vector params = new Vector();
    params.addElement(new Parameter(parameterString, String.class,   parameterObject ,Constants.NS_URI_SOAP_ENC));
call.setParams(params);
 
 

 Thanks
 
 
 
 

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