This seems to have fixed the GenericEnumUserType for me.  Very handy.
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public void nullSafeSet(PreparedStatement st, Object value, int index)
throws HibernateException, SQLException 
{
  try
  {
    if(value == null)
    {
      st.setObject(index, null);
    }
    else
    {
      Object identifier = identifierMethod.invoke(value, new Object[0]);
      type.set(st,identifier,index);
    }
  }
  catch (Exception exception)
  {
    throw new HibernateException("Exception while invoking
identifierMethod '" + identifierMethod + "' of enumeration class: '" +
enumClass + "'",exception);
  }
}