I am not deploying to a clustered environment but I am seeing the same error.
I have a JAX-WS web service created using NetBeans 6.5
The web service is deployed to Sun Java System Application Server 9.1_02 (build
b04-fcs) as a web application named "serviceForumWs".
The web service works but occasionally it logs the following:
In most cases I am aware of no ill effects and service appears to be unaffected
however on some occasions it coincides with the app server playing dead. On
these occasions it tends to appear some time after the app server dies and it is
the only entry in server.log until the app server is shut down and re-started.
I hope this helps