Brian,
If you look at any of the quickstarts, you see several files at the root of the folder: jbossesb-properties.xml, jndi.properties, and log4j.xml. This first tells the service invoker how to connect to the registry, and the second how to look up the JMS queue in the JNDI service. These need to be on the classpath of your ESB aware client, not inside the esbcontent folder. The esbcontent folder contains the files that get deployed in the esb archive to the server.