stou escrevendo um aplicativo Swing simples para a universidade e usando o Hibernate e o Oracle X

Estou preso com esse erro:

 29.06.2011 14:54:10 org.hibernate.cfg.annotations.Version <clinit>
 INFO: Hibernate Annotations 3.3.1.GA
 29.06.2011 14:54:10 org.hibernate.cfg.Environment <clinit>
 INFO: Hibernate 3.2.5
 29.06.2011 14:54:10 org.hibernate.cfg.Environment <clinit>
 INFO: hibernate.properties not found
 29.06.2011 14:54:10 org.hibernate.cfg.Environment buildBytecodeProvider
 INFO: Bytecode provider name : cglib
 29.06.2011 14:54:10 org.hibernate.cfg.Environment <clinit>
 INFO: using JDK 1.4 java.sql.Timestamp handling
 29.06.2011 14:54:10 org.hibernate.ejb.Version <clinit>
 INFO: Hibernate EntityManager 3.3.2.GA
 29.06.2011 14:54:31 org.hibernate.ejb.packaging.PersistenceXmlLoader$ErrorLogger warning
 WARNING: Warning parsing XML: XML InputStream(2) schema_reference.4: Failed to read schema document 'http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd', because 1) could not find the document; 2) the document could not be read; 3) the root element of the      document is not <xsd:schema>.
 29.06.2011 14:54:52 org.hibernate.ejb.packaging.PersistenceXmlLoader$ErrorLogger warning

my persistence.xml:

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">
  <persistence-unit name="airportPU">
    <provider>org.hibernate.ejb.HibernatePersistence</provider>
    <class>my.airport.model.Crew</class>
    <class>my.airport.model.Country</class>
    <class>my.airport.model.City</class>
    <class>my.airport.model.Plane</class>
    <class>my.airport.model.Model</class>
    <class>my.airport.model.Passenger</class>
    <class>my.airport.model.Role</class>
    <class>my.airport.model.Airport</class>
    <class>my.airport.model.Spec</class>
    <class>my.airport.model.AverageFlightTime</class>
    <class>my.airport.model.CrewInTheRoleOnTheFlight</class>
    <class>my.airport.model.Flight</class>
    <class>my.airport.model.PassengersOnTheFlight</class>
    <properties>     
      <property name="javax.persistence.jdbc.url" value="jdbc:oracle:thin:@172.16.0.3:1521:XE"/>
      <property name="javax.persistence.jdbc.password" value="AIRPORT"/>
      <property name="javax.persistence.jdbc.driver" value="oracle.jdbc.OracleDriver"/>
      <property name="javax.persistence.jdbc.user" value="AIRPORT"/>
    </properties>
  </persistence-unit>
</persistence>

riando fábrica de gerenciador de entidades:

public static EntityManagerFactory emf;
public static EntityManager em;
static {
try {
    emf = Persistence.createEntityManagerFactory("airportPU");
    em = emf.createEntityManager();
} catch (Exception e) {     
    System.exit(1);
}
}