The org.jboss.mx.remote.* packages and related classes are going away after the JBoss Remoting refactor. The new base level remoting classes are now in their own remoting module, jboss-remoting. The related MX classes are now in the package org.jboss.mx.remoting.*.
The JBoss-remoting classes are now part of the main server lib and available to all mbeans, etc.
Please update any code that depends on this package ASAP. I think the TX stuff is using the old InstanceID class - this should be replaced by the class org.jboss.remoting.ident.Identity (and call getInstanceId()) to get the unique server id of the server. NOTE: this id persists beyond reboots and will be the same! (unless you pass in the property -Djboss.identity or remove the file under data with the same name). You can call getJMXId() to get the JMX ServerID attribute on Identity.
If you have any questions, concerns, please email me directly as I'd like to do this remote ASAP.