cakePHP:偶发“对非对象调用成员函数allow()”

when I call a specifical controller-script of my Web-Application I sporadically get the following error:

Fatal error: Call to a member function allow() on a non-object in /srv/www/vhost/app/Controller/myController.php on line 11

Line 11 contains
$this->Auth->allow(array('get'));

Anyone an idea what this may cause?

Regards,
~MxAgent

Problem fixed. It was a caching-problem due to server doesn't support APC.