Did you set the pool for connection validation? If not, even if the JDK timer expires (this is what causes the container to start its part), the container will fail to verify the timer and fire the event. After the predefined number of attempts, the timer will be removed.
If the connection validation is on, please enable FINE logging in the EJB container see if there are any other clues what might've gone wrong.
-marina
[Message sent by forum member 'mvatkina' (marina.vatkina_at_sun.com)]
http://forums.java.net/jive/thread.jspa?messageID=386482