Hello,
 I've got the following issue with JBoss AS 5.0.0 Beta:
After I run a test (in "one-test" mode, so no previous test caused an time out etc.), I see on the server console that the corresponding jar is undeploying and the home interfaces are unbinding. But when I run the test again, I get InstanceAlreadyExistsException:

11:43:12,406 INFO  [Server] JBoss (MX MicroKernel) [5.0.0.Beta (build: CVSTag=HE
AD date=200608071122)] Started in 1m:3s:563ms
11:43:53,046 INFO  [EjbModule] Deploying Customer
11:43:53,234 INFO  [EjbModule] Deploying Account
11:43:53,250 INFO  [EjbModule] Deploying Teller
11:43:53,281 INFO  [EjbModule] Deploying Bank
11:43:54,687 INFO  [ProxyFactory] Bound EJB Home 'Customer' to jndi 'bank/Custom
er'
11:43:54,703 INFO  [ProxyFactory] Bound EJB Home 'Account' to jndi 'bank/Account
'
11:43:54,718 INFO  [ProxyFactory] Bound EJB Home 'Teller' to jndi 'bank/Teller'
11:43:54,734 INFO  [ProxyFactory] Bound EJB Home 'Bank' to jndi 'bank/Bank'
11:43:54,734 INFO  [EJBDeployer] Deployed: file:/D:/jboss-svn4/jboss-head/testsu
ite/output/lib/bank.jar
11:44:02,093 INFO  [EJBDeployer] Undeploying: file:/D:/jboss-svn4/jboss-head/tes
tsuite/output/lib/bank.jar
11:44:02,125 INFO  [ProxyFactory] Unbind EJB Home 'Bank' from jndi 'bank/Bank'
11:44:02,125 INFO  [EjbModule] Undeployed Bank
11:44:02,125 INFO  [ProxyFactory] Unbind EJB Home 'Teller' from jndi 'bank/Telle
r'
11:44:02,125 INFO  [EjbModule] Undeployed Teller
11:44:02,125 INFO  [ProxyFactory] Unbind EJB Home 'Account' from jndi 'bank/Acco
unt'
11:44:02,140 INFO  [EjbModule] Undeployed Account
11:44:02,140 INFO  [ProxyFactory] Unbind EJB Home 'Customer' from jndi 'bank/Cus
tomer'
11:44:02,140 INFO  [EjbModule] Undeployed Customer
*************
An now I run the test again:
*************
11:44:17,390 INFO  [EjbModule] Deploying Customer
11:44:17,421 INFO  [EjbModule] Deploying Account
11:44:17,421 INFO  [EjbModule] Deploying Teller
11:44:17,437 INFO  [EjbModule] Deploying Bank
11:44:17,453 INFO  [EntityContainer] Registration is not done -> stop
11:44:17,453 ERROR [AbstractKernelController] Error installing to Create: name=j
boss.j2ee:module=bank.jar,service=EjbModule,uid=29596937 state=Configured mode=M
anual requiredState=Create
javax.management.InstanceAlreadyExistsException: jboss.j2ee:jndiName=bank/Custom
er,service=EJB already registered.
        at org.jboss.mx.server.registry.BasicMBeanRegistry.add(BasicMBeanRegistr
y.java:765)
        at org.jboss.mx.server.registry.BasicMBeanRegistry.registerMBean(BasicMB
eanRegistry.java:234)
.
.
.
11:44:17,531 INFO  [EJBDeployer] Deployed: file:/D:/jboss-svn4/jboss-head/testsu
ite/output/lib/bank.jar
11:44:17,968 INFO  [EJBDeployer] Undeploying: file:/D:/jboss-svn4/jboss-head/tes
tsuite/output/lib/bank.jar
******************
I saw similar issues for previous versions of the AS (all resolved) but I think this is the first for the Beta 5.0 version.