I get the following error when trying to logout of my CakePHP app:
Notice (8): Undefined property: UsersController::$Session [APP/controllers/users_controller.ph
It looks like you don't have the Session component loaded in your Users controller.
The Session component should be loaded by default, but if you've set the components array in AppController this will overwrite the defaults.
This means that if you have
var $components = array();
in your AppController, make sure the Session component is included there:
var $components = array('Session');
Alternatively, you can load the Session component in your Users controller if you don't want to use it app-wide.