Bugs bugs bugs.

        'entity class' => 'Drupal/myentity/class/MyEntity',
        'controller class' => 'Drupal/myentity/controller/MyEntityController',

This should be

        'entity class' => 'Drupal\myentity\class\MyEntity',
        'controller class' => 'Drupal\myentity\controller\MyEntityController',


And:

    namespace Drupal\myentity\class\MyEntity;

This should be

    namespace Drupal\myentity\class;

(and btw, is "class" really a valid namespace part? Won't PHP complain?)

And:

    sites\all\modules\myentity\lib\Drupal\controller\MyEntityController.php

This should be:

    sites\all\modules\myentity\lib\Drupal\myentity\controller\MyEntityController.php