Tomcat Exception while Invoking Windchill java based web services

We have created java based web services in windchill. Its working fine when we ping service from Windchill shell. When we try to invoke the service using Websphere Message Broker (using wsdl of the web service as input), we got Authentication error. We found out that it was because we dint define the keystore properly. But even after defining the keystore and Certificates, we get the following exception in Tomcat :

Mar 28, 2011 4:56:47 PM com.sun.xml.ws.security.opt.impl.incoming.processor.SecurityTokenProcessor processDirectReference SEVERE: WSS1816: Error occurred while resolving Direct Reference

Any inputs or ideas on this??