You are using namespaces in your application, therefore you need to make sure that your autoloader can handle this. If it's a ZF1 app then not. Can you try using require to include the class file instead? You can ass well amend the autoloader to work with namespaces
Secondly when using namespaces, if you create an alias for a class
use Zend\Crypt\BlockCipher;
you then instantiate it
$blockCipher = BlockCipher::factory('mcrypt',array('algo'=>'aes'));