What happens:
When editing a node inside overlay Drupal.settings does not contains all settings.

Setup:
An element attaches JS settings inside hook_field_widget_form as the following

$element['ref_id'] = array('#type' => 'tableselect', '#header' => $headers, 
        '#options' => $options, '#default_value' => $default_value, 
        '#attributes' => array('id' => array('filterable-table')), 
        '#sticky' => TRUE, 
        '#attached' => array(
            'js' => array(
                array('data' => $jsPath . '/lib/jquery.dataTables.min.js', 
                    'type' => 'file'), 
                array('data' => $jsPath . '/lib/table.filter.js', 
                    'type' => 'file'), 
                array('data' => array('some_key' => array('value' => 3)), 
                    'type' => 'setting'))));
  }

NOTE:
Drupal.settings contains some_key setting, when node is not edited inside the overlay.

Comments

Version: 7.22 » 7.x-dev

Core issues are now filed against the dev versions where changes will be made. Document the specific release you are using in your issue comment. More information about choosing a version.