Ops... it seems that it is now 2861 - https://issues.jboss.org/browse/JBAS-2861
The best solution i found is to modify the session manager to ignore context names.
The current problem is that this is only possible after JBoss ORG 6.0.0 M2:
And i need it on EAP 5.1.1. But i guess that is easier to solve...