Actually, just run the tests locally with some TRACE logging and there appears to be a race condition between the @Start phases of Transport and Marshaller:

2009-07-23 12:08:12,300 5718 TRACE [org.infinispan.remoting.transport.jgroups.CommandAwareRpcDispatcher] (Incoming-1,Infinispan-Cluster,localhost.localdomain-45973 Problems invoking command.
java.lang.NullPointerException
at org.infinispan.marshall.jboss.JBossMarshaller$2.initialValue(JBossMarshaller.java:87)
...
2009-07-23 12:08:12,334 5752 INFO [org.infinispan.remoting.transport.jgroups.JGroupsTransport] (main Cache local address is localhost.localdomain-45973
2009-07-23 12:08:12,335 5753 DEBUG [org.infinispan.marshall.jboss.JBossMarshaller] (main Using JBoss Marshalling based marshaller.

Basically, JGroups transport is starting before Marshaller whereas it should be the other way around. Currently, both start methods where using priority=10.

Changing marshaller's priority to 9 appears to solve the issue