On Plugin atop Branch_5_x boot:

21:06:47,002 ERROR [AbstractKernelController] Error installing to Real: name=vfszip:/home/alrubinger/business/jboss/wc/jbossas/branches/Branch_5_x/build/output/jboss-5.1.0.CR1/server/all/deploy/jboss-ejb3-timerservice-as5.jar/ state=PreReal mode=Manual requiredState=Real
org.jboss.deployers.spi.DeploymentException: Error deploying: JBossTimerServiceFactory
...
Caused by: java.lang.IllegalStateException: JBossTimerServiceFactory is already installed.

...this causes regression in the EJB3 Integration TestSuite "ejbthree1624":

Caused by: java.lang.RuntimeException: Could not lookup object at name "testMcBean" due to an error with the underlying ControllerContext