Module settings are not showing up

I forgot to say I am using the development snapshot from November 7; if the code has been already changed, and I need to wait 1 hour to get the new archive, then I apologize for this report.

The line for which the error is report is contained in the following function:

function vertical_tabs_node_type_form(&$form, $node_type) {
  module_load_include('inc', 'node', 'node.pages');

  // Build a psuedo-node for a sample node form.
  $node = (object) array(
    'type' => $node_type,
    'name' => '',
    'vid' => 0,
  );

  // Build a sample node form to find fieldsets.
  $node_form_state = array('values' => array());
  $node_form_id = $node_type .'_node_form';
  $args = array(
    $node_form_id,
    $node_form_state,
    $node
  );
  $node_form = call_user_func_array('drupal_retrieve_form', $args);
  $node_form['#post'] = $node_form_state['values'];
  drupal_prepare_form($node_form_id, $node_form, $node_form_state);
  uasort($node_form, 'element_sort');

  // Find all fieldsets.
  $fieldsets = array();
  foreach (element_children($node_form) as $key) {
    if (isset($node_form[$key]['#type']) && $node_form[$key]['#type'] == 'fieldset' && isset($node_form[$key]['#title'])) {
      $fieldsets[$key] = $node_form[$key]['#title'];
    }
  }

  $form['vertical_tabs'] = array(
    '#type' => 'fieldset',
    '#title' => t('Vertical tabs'),
    '#collapsible' => TRUE,
    '#collapsed' => TRUE,
    '#description' => t('The selected fieldsets will be rendered as vertical tabs for this content type. The tabs are rendered in the same version as the original form\'s fieldsets.'),
  );
  $form['vertical_tabs']['vertical_tabs_fieldsets'] = array(
    '#type' => 'checkboxes',
    '#options' => $fieldsets,
    '#default_value' => vertical_tabs_fieldsets($node_type),
  );
}

The line that causes the error I reported contains $node_form = call_user_func_array('drupal_retrieve_form', $args).

As last note, I am having the issue on Mac OS X 10.6, which runs PHP 5.3.0.