Obtaining SecurityManagerService failed jboss4.x

[mikedanese]

my web app is running as a simple war file under tomcat, configured for https
Authentication is being handled via servlet. I am getting (sometimes, unpredicatbly) error which is preventing user login. jboss-web.xml declares:
< security-domain flushOnSessionInvalidation="false" >
Somewhere I read to remove the 'flush.. ' attribute??
Any tips appreciated.

partial stack trace:
2006-11-29 13:13:50,816 DEBUG [org.jboss.web.tomcat.security.SecurityFlushSessionListener] Obtaining SecurityManagerService failed::
java.lang.ClassCastException: org.jnp.interfaces.NamingContext
at org.jboss.web.tomcat.security.SecurityFlushSessionListener.getSecurityManagerService(SecurityFlushSessionListener.java:193)
at org.jboss.web.tomcat.security.SecurityFlushSessionListener.getSubjectAndSecurityDomain(SecurityFlushSessionListener.java:160)
at org.jboss.web.tomcat.security.SecurityFlushSessionListener.sessionDestroyed(SecurityFlushSessionListener.java:79)
at org.apache.catalina.session.StandardSession.expire(StandardSession.java:687)
at org.apache.catalina.session.StandardSession.isValid(StandardSession.java:579)
at org.apache.catalina.session.ManagerBase.processExpires(ManagerBase.java:678)
at org.apache.catalina.session.ManagerBase.backgroundProcess(ManagerBase.java:663)
at org.apache.catalina.core.ContainerBase.backgroundProcess(ContainerBase.java:1284)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1569)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1578)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1578)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1558)
at java.lang.Thread.run(Thread.java:595)
2006-11-29 13:13:50,822 DEBUG [org.jboss.web.tomcat.security.SecurityFlushSessionListener] Unable to obtain SecurityDomain
2006-11-29 14:03:54,485 DEBUG [org.jboss.web.tomcat.security.SecurityFlushSessionListener] Obtaining SecurityManagerService failed::
java.lang.ClassCastException: org.jnp.interfaces.NamingContext

[starksm64]

You most likely have jboss jars in you web app. There should never be any jboss server jars in application deployments.