This issue is probably not related only to the ACEGI plugin (in fact I'm 100% certain it is not) but it seems like the tcServer does not work as a container in a load balanced configuration. Tomcat 5.5 does. I spent hours trying to figure out why tcServer was not working but if anyone else encounters a problem where the logins work when you have a single instance but stop working when you start load balancing, then simply switch to Tomcat and that should solve it.