If you are trying the tutorials with the EJB 3.0 preview and the JBoss 1.5 preview and are getting ClassCastExceptons on the org.jboss.ejb3.remoting class:
The jars in the IDE's eclipse\plugins\org.jboss.ide.eclipse.ejb3.wizards.core_1.4.9 folder need to be updated with the matching jars in the jboss-EJB-3.0_Preview_3\lib\ejb3.deployer folder.
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jboss-EJB-3.0_Preview_3\lib\ejb3.deployer
jboss-ejb3.jar
jboss-ejb3x.jar
Copy to plugin folder-->
eclipse\plugins\org.jboss.ide.eclipse.ejb3.wizards.core_1.4.9
