Have a look inside the persistence.properties file ($JBOSS_HOME/server/all/deploy/ejb3.deployer/META-INF/persistence.properties) and change
In other words comment out the create-drop line. If you like try out the create line to create the initial schema for you.
That was the problem! After edit persistence.properties as you told, the problem ends.
Thank you very much!
Another, probably preferred, method would be to include a persistence.xml file in the META-INF folder within your ejb3 / jar file. Have a look at
http://trailblazer.demo.jboss.com/EJB3Trail/persistence/config/ for more information on how to do this.