I have created a MBean which extends the ServiceMBeanSupport class and placed an entry into the jboss-service.xml file. All run's well. (I have placed all my classes within a simple JAR within server/default/lib.)
Next I created my own MBean independent of JBoss. I created an instance of the MBean within my JBoss MBean metioned above and register it with the server given to me by the JBoss MBean Services.