hook_menu/MENU_CALLBACK access denied
I tested out the hook_menu in my local. The hook seems fine. Check if you have added an  access denied code in the callback function


function commons_menu() {
  $items = array();
   $items['data/update'] = array(
    'page callback' => 'dataupdate',
    'access callback' => TRUE,
    'type' => MENU_CALLBACK,
  );
   $items['onthewayout/forward'] = array(
    'page callback' => 'register_click',
    'access callback' => TRUE,
    'type' => MENU_CALLBACK,
  );
  return $items;
}

function dataupdate() {
  return drupal_set_message("First one is working");
}

function register_click() {
  return drupal_set_message("Second one is also working");
}




This returns a Access Denied to me even if access callback is true.


function register_click() {
  drupal_access_denied();
  exit;
}