java.lang.IllegalStateException: No security context set
 at org.jboss.ejb.EnterpriseContext$EJBContextImpl.getCallerPrincipal(EnterpriseContext.java:276)

I get the above error when doing a stress test on my web services layer. It pops about two times for every one hundred transactions. It is not consistent. I have

<security-domain>java:/jaas/ActiveChain-login</security-domain>

set in the jboss.xml, and my web-service.xml looks like this.

<requestFlow name="locationServicesRequest">
 <handler type="java:org.jboss.net.axis.server.JBossAuthenticationHandler">
 <parameter name="securityDomain" value="java:/jaas/ActiveChain-login"/>
 </handler>
 <handler type="java:org.jboss.net.axis.server.JBossAuthorizationHandler">
 <parameter name="securityDomain" value="java:/jaas/ActiveChain-login"/>
 <parameter name="allowedRoles" value="users"/>
 </handler>

 </requestFlow>

Any help would be greatly appreciated, it's these inconsistant ones that drive me mad.