The .name() change from toString() was a good one, but there's a missing
case.. NullSafeSet should look like:

public void nullSafeSet(PreparedStatement preparedStatement, Object
value, int index) 
  throws HibernateException, SQLException {

  if (null == value) {
    preparedStatement.setNull(index, Types.VARCHAR);
  } else {
    preparedStatement.setString(index, ((Enum)value).name());
  }
}