Invalid controller specified (a)

Arquivo /home/otto/library/Zend/Controller/Dispatcher/Standard.php, linha 248

Trace #0 /home/otto/library/Zend/Controller/Front.php(954): Zend_Controller_Dispatcher_Standard->dispatch(Object(Zend_Controller_Request_Http), Object(Zend_Controller_Response_Http)) #1 /home/otto/library/Zend/Application/Bootstrap/Bootstrap.php(97): Zend_Controller_Front->dispatch() #2 /home/otto/library/Zend/Application.php(366): Zend_Application_Bootstrap_Bootstrap->run() #3 /home/otto/public_html/index.php(32): Zend_Application->run() #4 {main}