Hey I got this when undeploying on DR2. Very cool sample, though.

02:47:13,671 INFO [MainDeployer] Undeploying file:/C:/jboss/jboss-4.0.0DR2/serv
er/default/deploy/jbossdo-example.war
02:47:13,741 INFO [EmbeddedCatalinaService41] undeploy, ctxPath=/jbossdo-exampl
e, warUrl=file:/C:/jboss/jboss-4.0.0DR2/server/default/tmp/deploy/server/default
/deploy/jbossdo-example.war/62.jbossdo-example.war/
02:47:15,183 INFO [DeploymentInfo] undeployment exception in stop:
org.jboss.deployment.DeploymentException: Error during deploy; - nested throwabl
e: (java.lang.NullPointerException)
at org.jboss.web.AbstractWebContainer.stop(AbstractWebContainer.java:503
)
at org.jboss.deployment.DeploymentInfo.stop(DeploymentInfo.java:269)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.
java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAcces
sorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:324)
at org.jboss.mx.server.ReflectedDispatcher.dispatch(ReflectedDispatcher.
java:72)
at org.jboss.mx.server.Invocation.dispatch(Invocation.java:45)
at org.jboss.mx.server.Invocation.invoke(Invocation.java:70)
at org.jboss.mx.server.AbstractMBeanInvoker.invoke(AbstractMBeanInvoker.
java:155)
at org.jboss.mx.server.MBeanServerImpl.invoke(MBeanServerImpl.java:544)
at org.jboss.system.ServiceController$ServiceProxy.invoke(ServiceControl
ler.java:1036)
at $Proxy14.stop(Unknown Source)
at org.jboss.system.ServiceController.stop(ServiceController.java:478)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.
java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAcces
sorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:324)
at org.jboss.mx.server.ReflectedDispatcher.dispatch(ReflectedDispatcher.
java:72)
at org.jboss.mx.server.Invocation.dispatch(Invocation.java:45)
at org.jboss.mx.server.Invocation.invoke(Invocation.java:70)
at org.jboss.mx.server.AbstractMBeanInvoker.invoke(AbstractMBeanInvoker.
java:155)
at org.jboss.mx.server.MBeanServerImpl.invoke(MBeanServerImpl.java:544)
at org.jboss.deployment.MainDeployer.stop(MainDeployer.java:838)
at org.jboss.deployment.MainDeployer.undeploy(MainDeployer.java:507)
at org.jboss.deployment.MainDeployer.undeploy(MainDeployer.java:502)
at org.jboss.deployment.MainDeployer.undeploy(MainDeployer.java:446)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.
java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAcces
sorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:324)
at org.jboss.mx.server.ReflectedDispatcher.dispatch(ReflectedDispatcher.
java:72)
at org.jboss.mx.server.Invocation.dispatch(Invocation.java:45)
at org.jboss.mx.server.Invocation.invoke(Invocation.java:70)
at org.jboss.mx.server.AbstractMBeanInvoker.invoke(AbstractMBeanInvoker.
java:155)
at org.jboss.mx.server.MBeanServerImpl.invoke(MBeanServerImpl.java:544)
at org.jboss.util.jmx.MBeanProxy.invoke(MBeanProxy.java:172)
at $Proxy9.undeploy(Unknown Source)
at org.jboss.deployment.scanner.URLDeploymentScanner.undeploy(URLDeploym
entScanner.java:435)
at org.jboss.deployment.scanner.URLDeploymentScanner.scan(URLDeploymentS
canner.java:507)
at org.jboss.deployment.scanner.AbstractDeploymentScanner$ScannerThread.
doScan(AbstractDeploymentScanner.java:200)
at org.jboss.deployment.scanner.AbstractDeploymentScanner$ScannerThread.
loop(AbstractDeploymentScanner.java:211)
at org.jboss.deployment.scanner.AbstractDeploymentScanner$ScannerThread.
run(AbstractDeploymentScanner.java:190)
Caused by: java.lang.NullPointerException
at org.jboss.web.catalina.EmbeddedCatalinaService41.performUndeploy(Embe
ddedCatalinaService41.java:316)
at org.jboss.web.AbstractWebContainer.stop(AbstractWebContainer.java:492
)
... 42 more
02:47:15,554 INFO [MainDeployer] Undeployed file:/C:/jboss/jboss-4.0.0DR2/serve
r/default/deploy/jbossdo-example.war
02:47:15,554 INFO [MainDeployer] Undeploying file:/C:/jboss/jboss-4.0.0DR2/serv
er/default/deploy/jbossdo-example.jar
02:47:15,554 INFO [PersistenceManagerFactoryImpl] Stopping jboss.jbossdo:JndiNa
me=java%3a/PersistenceManagerFactory,service=PersistenceManagerFactory
02:47:15,574 INFO [JDOModule] Stopping jboss.jbossdo:service=JDOModule,url=file
%3a/C%3a/jboss/jboss-4.0.0DR2/server/default/deploy/jbossdo-example.jar
02:47:15,604 INFO [MainDeployer] Undeployed file:/C:/jboss/jboss-4.0.0DR2/serve
r/default/deploy/jbossdo-example.jar