Error after ejbPassivate

[try catch]

Hi All!
I've a Statefull Session Bean acting as a Session Facade.
Why after a call to ejbPassivate() by JBoss, a subsequent call to ejbActivate() wich access to the SessionContext object throws this exception:
java.lang.IllegalStateException: No security context set
at org.jboss.ejb.EnterpriseContext$EJBContextImpl.getCallerPrincipal
(EnterpriseContext.java:276)
at sit.ejb.SessionFacadeBean.ejbActivate(SessionFacadeBean.java:53)

Help me, pleeeease!!!
[ July 20, 2004: Message edited by: try catch ]