[PersistenceUnit: Hibernate] Unable to configure EntityManagerFactory

Menssagen menssagen = new Menssagen();
		menssagen.setTexto(".....");
		
		
		EntityManagerFactory emf = Persistence.createEntityManagerFactory("Hibernate");
		EntityManager em = emf.createEntityManager();
		EntityTransaction tx = em.getTransaction();
		tx.begin();
		
		em.persist(menssagen);
		
		tx.commit();
		em.close();

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="1.0"
	xmlns="http://java.sun.com/xml/ns/persistence">
	<persistence-unit name="Hibernate">
		<provider>org.hibernate.ejb.HibernatePersistence</provider>
		<class>br.com.hibernate.Menssagen</class>
		<properties>
			<property name="hibernate.dialect" value="org.hibernate.dialect.PostgreSQLDialect" />
			<property name="hibernate.connection.url" value="jdbc:postgresql://localhost/postgres" />
			<property name="hibernate.connection.driver_class" value="org.postgresql.Driver" />
			<property name="hibernate.connection.password" value="postgres" />
			<property name="hibernate.connection.username" value="" />
			<property name="hibernate.hbm2ddl.auto" value="create-drop" />
		</properties>
	</persistence-unit>
</persistence>