I have an almost similar problem. I use JBoss 4.2.2. I have removed jaxws-rt.jar and jaxws-tools.jar from the client directory, and copied the xercesImpl.jar into it from the lib/endorsed directory, as described in this thread. I have also copied the It still fails with; javax.xml.ws.WebServiceException: Unable to load Provider: Failed to load javax.xml.ws.spi.Provider: com.sun.xml.ws.spi.ProviderImpl at javax.xml.ws.spi.Provider.provider(Provider.java:98) at javax.xml.ws.Service.(Service.java:83) Caused by: java.lang.IllegalStateException: Failed to load javax.xml.ws.spi.Provider: com.sun.xml.ws.spi.ProviderImpl at javax.xml.ws.spi.ProviderLoader.loadProvider(ProviderLoader.java:96) at javax.xml.ws.spi.Provider.provider(Provider.java:90) Caused by: java.lang.NoClassDefFoundError at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39) Can anyone tell me what I'm doing wrong ?? View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4170535#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...