If you noticed something weird at howforge.com, 404 file not found was missing. Instead, it was replaced by 403 access denied. The cause of this problem is exactly adsense.module. Let me show you something.

function adsense_menu($may_cache) { 
  $items = array();
 
  if ($may_cache) {
    $items[] = array(
      ’path’     => ’’,
      ’callback’ => ’’,
      ’title’    => ’’,
      ’access’   => user_access(’hide adsense’),
      ’type’     => MENU_CALLBACK,
      ’weight’   => 0);
   }
   return $items;
}

This menu hooking is totally incorrect. The empty path makes all page not found errors replaced by access denied errors. To fix this problem, I simply commented this function out. The patch is as below and also submitted at drupal.org.