JBOSS AS 4.2.3.GA  java.lang.NullPointerException at org.jboss.ejb.txtimer.DatabasePersistencePolicy.listTimerHandles(DatabasePersistencePolicy.java:165)  I've solved CLEANING UP  the folowing dirs: jboss/server/default/tmp jboss/server/default/data jboss/server/default/work but there are other issues that can happen, if that's the case follow:
https://jira.jboss.org/jira/browse/JBPORTAL-1855  http://www.guj.com.br/posts/list/91367.java  http://www.techienuggets.com/Detail?tx=12989  http://markmail.org/message/xqioiwxqrjbkr5hv  http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4100705#4100705
Good Luck!