Magento自定义选项卡网格与Ajax网格错误

I want to add custom edit tabs for magento backend admin. i have been following some tutorial, from :

• http://inchoo.net/magento/magento-grid-serializer-ajax-grids/
• http://excellencemagentoblog.com/blog/2011/09/07/magento-grid-serializer-admin-tabs-grid/

but I always have same result : Fatal error: Call to a member function setSelectedCustomers() on boolean in controller.php

Is there something wrong? Help me to solve this problem, please. :)

SOLVED

• I forgot to inclue layout in config.xml
• clear cache