Symfony: PHP class not found when loading Appbundle in Appkernel.php

Question

For some weird reason my App and ApiBundle Classes are not found during registerbundles()-function of Appkernel.php.

The classes are there and seeem to be correct and I cannot understand what the problem is.

Appkernel-entries:

    new Neulich\AppBundle\NeulichAppBundle(),
    new Neulich\ApiBundle\NeulichApiBundle(),

Neulich/src/AppBundle/NeulichAppBundle.php:

<?php

namespace Neulich\AppBundle;

use Symfony\Component\HttpKernel\Bundle\Bundle;

/**
 * Class NeulichAppBundle
 *
 * @package Neulich\AppBundle
 */
class NeulichAppBundle extends Bundle
{
}

Please give me a hint, I've been trying for a long time now.

Thanks a lot. Steffen