Authenticated users cannot access /sitemap.xml

Because

  $items['sitemap.xml'] = array(
    'title' => 'Site map index',
    'page callback' => 'xmlsitemap_output',
    'access callback' => 'xmlsitemap_anonymous_access',
    'type' => MENU_CALLBACK,
  );

and then this returns FALSE for authenticated users

function xmlsitemap_anonymous_access() {
  global $user;
  return $user->uid == 0;
}

Changing the above to

function xmlsitemap_anonymous_access() {
  return TRUE;
}

allows all to be able to access the sitemap but so will this change

  $items['sitemap.xml'] = array(
    'title' => 'Site map index',
    'page callback' => 'xmlsitemap_output',
    'access callback' => TRUE,
    'type' => MENU_CALLBACK,
  );

based on the review of the code at http://api.drupal.org/api/function/_menu_check_access/6 and my testing.

Patch is based on the menu change.