Hi,
We can easily reproduce the problem in Tomcat by just reference the PortalClusteredSSOSupportValve class in a Servlet Context listener of a web app, to load it.
I can see that it has been changed in org.apache.catalina.valves.ValveBase since Tomcat API 7.0 which already defined a final start() method from its indirect parent class org.apache.catalina.util.LifecycleBase
http://tomcat.apache.org/tomcat-7.0-doc/api/org/apache/catalina/valves/ValveBase.html
I confirmed that the problem doesn't happen in JBoss, so I guess this api part is not consistent between Tomcat and JBossWeb.
In addition, there is no error in compile time as it is using tomcat catalina version 6.0.29 declared in gatein-dep.
Thanks,