We had a similar error... the issue was with our ejb-jar.xml file.
Take a look at how jboss loads your jar file.
For example:
review the server.log for how your jar file is loaded. Notice the name mismatch in mine RefundPolicyRequestPlugin vs RefundPolicyPlugin
2011-12-14 19:12:56,394 INFO [org.jboss.ejb.deployers.EjbDeployer] installing bean: ejb/RefundPolicyRequestPlugin.jar#RefundPolicyPlugin,uid1280009145
2011-12-14 19:12:56,395 INFO [org.jboss.ejb.deployers.EjbDeployer] with dependencies:
2011-12-14 19:12:56,395 INFO [org.jboss.ejb.deployers.EjbDeployer] and supplies:
2011-12-14 19:12:56,395 INFO [org.jboss.ejb.deployers.EjbDeployer] jndi:RefundPolicyPlugin
Our error was with our ejb-jar.xml file (we changed the name to RefundPolicyRequestPlugin and failed to change the ejb-jar.xml file
<enterprise-beans>
<session>
<ejb-name>RefundPolicyPlugin</ejb-name>
JBOSS 5 and 6 are more restrictive in their naming then jboss 4 was. Hope this helps.