For all those who encounter this issue: try to know if you're deploying a webapp that has its own log4j.jar Since JBoss has already a log4j.jar, you can obtain this error if both versions are not the same. Just remove log4j.jar from you webapp's WEB-INF/lib when deploying (an exclude might be enough in your ant file) Take a look to the lasts posts here: http://www.dcm4che.org/jira/browse/OV-28?focusedCommentId=10959#action_10959 View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4141425#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...