Help : Hibernate class with many-to-one don't save-update/commit

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
   <class name="heuresEffectuees.HeuresEffectuees" table="heuresEffectuees">
      <composite-id>
         <key-property name="noBon"/>
         <key-property name="cipRepondant"/>
      </composite-id>
      <property name="nbHeuresEffectuees"/>
      <many-to-one name="repondant" column="cipRepondant" class="repondants.Repondant" lazy="false" insert="false" update="false"/>
   </class>
</hibernate-mapping>

public class HeuresEffectueesDAO {
   Session currentSession() {
      return HibernateUtil.currentSession();
   }

   //!!!!!!!!     DON’T WORK   !!!!!!!!
   public void saveOrUpdate(HeuresEffectuees desHeuresEffectuees) {
      Session sess = currentSession();
      sess.saveOrUpdate(desHeuresEffectuees);      
   }

   //!!!!!!!!!!!!    WORK    !!!!!!!!!!!
   public void saveOrUpdate2(HeuresEffectuees desHeuresEffectuees) {
      Session sess = currentSession();
      Transaction tx = sess.beginTransaction();
      sess.saveOrUpdate(desHeuresEffectuees);
      tx.commit();
   }

   public void delete(HeuresEffectuees desHeuresEffectuees) {
      Session sess = currentSession();
      sess.delete(desHeuresEffectuees);
   }
   
   public List findAllByNoBon(String noBon) {
      Session sess = currentSession();      
      Criteria criteria = sess.createCriteria(HeuresEffectuees.class);
      criteria.add(Restrictions.like("noBon", noBon));      
      return criteria.list();      
   }

   public HeuresEffectuees findByNoBonEtRepondant(String noBon, String cipRepondant) {
      Session sess = currentSession();
      return (HeuresEffectuees) sess.get(HeuresEffectuees.class, cipRepondant);
   }

   public List findAll() {
      Session sess = currentSession(); 
      return sess.createQuery("from HeuresEffectuees").list();
   }
}

         public class HeuresEffectueesRowRenderer implements RowRenderer {
            public void render ( Row row, Object data ){
               //if i access repondant then i can't save-update a new HeuresEffectuees.
               new Label(((HeuresEffectuees)data).getRepondant().getNom()).setParent(row);
               new Label(((HeuresEffectuees)data).getNbHeuresEffectuees().toString()).setParent(row);               
               new Label("").setParent(row);
            }
         }