Module does not seem to respect page title overrides

While other reg / login page titles can be altered with the following code, any reg form created with this module cannot be overridden.

function MyTheme_preprocess_page(&$variables) { 

  if (arg(0) == 'user') { // This function sets custom page titles for the user pages
    switch (arg(1)) {
      case NULL:
        if (!user_is_logged_in()) drupal_set_title(t('Log in'));
        break;
      case '[arg 2 of the path set for custom reg form]':
        drupal_set_title(t('Title that can't be set'));
        break;
      case 'register':
        drupal_set_title(t('Register'));
        break;
      case 'password':
        drupal_set_title(t('Request new password'));
        break;
      case 'login':
        drupal_set_title(t('Log in'));
        break;
    }
  }
}