"first parameter must either be an object or the name of an existing class" on line 552 of "user.module"

Full Message:

First parameter must either be an object or the name of an existing class File /home/quickstart/websites/sid.dev/modules/user/user.module, line 552
Processed 1 (0 created, 0 updated, 1 failed, 0 ignored) in 0.1 sec (1074/min) - done with 'SIDstaffContent'

I receive this when trying the import...
my class looks like this:

class SIDstaffContentMigration extends Migration {

  public function __construct() {

    parent::__construct();
    
    $this->description = t('Migrate SID content from csv file');
    
    $columns[0] = array('id_csv', 'Unique ID');
    $columns[1] = array('name', 'name');
    $columns[2] = array('mail', 'mail');   
    
    $this->source = new MigrateSourceCSV(drupal_get_path('module', 'migrate_sid').'/csv/tbl_staff.csv', $columns);
    
    $this->destination = new MigrateDestinationUser();
    
    $this->map = new MigrateSQLMap($this->machineName,
        array(
          'id_csv' => array('type' => 'varchar',
                            'length' => 255,
                            'not null' => TRUE,
                            'description' => 'Unique ID',
                            )
        ),
      MigrateDestinationUser::getKeySchema()
    );
    
    //standard fields
    $this->addFieldMapping('uid', 'id_csv');
    $this->addFieldMapping('name', 'fullname');
    $this->addFieldMapping('mail', 'mail');
    
    //all the fields we don’t wanna map in the destination!!!
      $this->addFieldMapping('pass') 
      ->issueGroup(t('DNM'));
    $this->addFieldMapping('theme') 
      ->issueGroup(t('DNM'));
    $this->addFieldMapping('signature') 
      ->issueGroup(t('DNM'));	  
    $this->addFieldMapping('signature_format') 
      ->issueGroup(t('DNM'));
    $this->addFieldMapping('created') 
      ->issueGroup(t('DNM'));	  
    $this->addFieldMapping('access') 
      ->issueGroup(t('DNM'));
    $this->addFieldMapping('login') 
      ->issueGroup(t('DNM'));  
    $this->addFieldMapping('status') 
      ->issueGroup(t('DNM'));  
    $this->addFieldMapping('timezone') 
      ->issueGroup(t('DNM'));
    $this->addFieldMapping('language') 
      ->issueGroup(t('DNM'));	
    $this->addFieldMapping('picture') 
      ->issueGroup(t('DNM'));	  
    $this->addFieldMapping('init') 
      ->issueGroup(t('DNM'));	
    $this->addFieldMapping('data') 
      ->issueGroup(t('DNM'));
  

  }