I am deploying my application to Tomcat 6.0.20.
Application uses Hibernate as ORM, Spring, and JSF for web-tier.
I also made simple runner from main() method
I solved it by excluding dom4j from hibernate entitymanager.
Also make sure you do mvn clean before.
mvn clean
org.hibernate hibernate-entitymanager 4.1.5.SP1 compile dom4j dom4j