maybe you could post your complete .wsdd file because i don't see any "urn:Addresschecker" in your file. for example if you decide to use xmlns:ns1="urn:Addresschecker" as namespace instead of doing something like xmlns:ns1="http://mypackage.something" then you should do :
<beanMapping xmlns:ns1="urn:Addresschecker" qname="ns1:ReturnValue" languageSpecificType="java:mypackage.ReturnValue"/> thus in your client class you should do: QName myQn = new QName("urn:Addresschecker", "ReturnValue"); call.registerTypeMapping(mypackage.ReturnValue.class, myQn, new org.apache.axis.encoding.ser.BeanSerializerFactory(mypackage.ReturnValue.cla ss, myQn), new org.apache.axis.encoding.ser.BeanDeserializerFactory(mypackage.ReturnValue.c lass, myQn)); instead of: <beanMapping xmlns:ns1="http://mypackage.something" qname="ns1:ReturnValue" languageSpecificType="java:mypackage.ReturnValue"/> and client code : QName myQn = new QName("http://mypackage.something", "ReturnValue"); call.registerTypeMapping(mypackage.ReturnValue.class, myQn, new org.apache.axis.encoding.ser.BeanSerializerFactory(mypackage.ReturnValue.cla ss, myQn), new org.apache.axis.encoding.ser.BeanDeserializerFactory(mypackage.ReturnValue.c lass, myQn));