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