Also, the JBoss Cache instance used for HttpSession replication and ClusteredSSO is configured for asynchronous replication. This means it is possible for an SSO to be started on one server and then that server dies before the SSO is replicated. The heavier the load, the greater the possibility, although still not high.
thanks for the reply !
I checked the JIRA you linked. Not sure which of the two problems is showing up, but I guess that it is one of them and knowing that all is ok.
I belive that it could be due to the load, since I am stressing the AS somewhat and it is running in a XEN with two virtuell pc's. Since there are NAKACK messages showing up, the load seems to be very likely for causing this.
2006-09-25 18:31:43,490 WARN [org.jgroups.protocols.pbcast.NAKACK] [06-2:34224] discarded message from non-member 06-1:33572