White Page in manager after upgrade

[fabryshock]

Hi i have upraded magento to the last 1.9 version. Unfortunally all work in front end but when i go in index.php/admin i get this error:

Method "addCustomLayoutHandle" is not defined in "WP_OnePageCheckout_Model_Config_Observer"

#0 C:\xampp\htdocs\ceunmondo\app\code\core\Mage\Core\Model\App.php(1360): Mage::throwException('Method "addCust...')
#1 C:\xampp\htdocs\ceunmondo\app\code\core\Mage\Core\Model\App.php(1337): Mage_Core_Model_App->_callObserverMethod(Object(WP_OnePageCheckout_Model_Config_Observer), 'addCustomLayout...', Object(Varien_Event_Observer))
#2 C:\xampp\htdocs\ceunmondo\app\Mage.php(448): Mage_Core_Model_App->dispatchEvent('controller_acti...', Array)
#3 C:\xampp\htdocs\ceunmondo\app\code\core\Mage\Core\Controller\Varien\Action.php(302): Mage::dispatchEvent('controller_acti...', Array)
#4 C:\xampp\htdocs\ceunmondo\app\code\core\Mage\Core\Controller\Varien\Action.php(259): Mage_Core_Controller_Varien_Action->loadLayoutUpdates()
#5 C:\xampp\htdocs\ceunmondo\app\code\core\Mage\Adminhtml\Controller\Action.php(275): Mage_Core_Controller_Varien_Action->loadLayout(NULL, true, true)
#6 C:\xampp\htdocs\ceunmondo\app\code\core\Mage\Adminhtml\controllers\IndexController.php(81): Mage_Adminhtml_Controller_Action->loadLayout()
#7 C:\xampp\htdocs\ceunmondo\app\code\core\Mage\Core\Controller\Varien\Action.php(418): Mage_Adminhtml_IndexController->loginAction()
#8 C:\xampp\htdocs\ceunmondo\app\code\core\Mage\Core\Controller\Varien\Router\Standard.php(254): Mage_Core_Controller_Varien_Action->dispatch('login')
#9 C:\xampp\htdocs\ceunmondo\app\code\core\Mage\Core\Controller\Varien\Front.php(172): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
#10 C:\xampp\htdocs\ceunmondo\app\code\core\Mage\Core\Model\App.php(365): Mage_Core_Controller_Varien_Front->dispatch()
#11 C:\xampp\htdocs\ceunmondo\app\Mage.php(684): Mage_Core_Model_App->run(Array)
#12 C:\xampp\htdocs\ceunmondo\index.php(84): Mage::run('', 'store')
#13 {main}

 Any help is very helpfull!!

[Agypten]

Most likely your custom module does not support version 1.9. Magento. Go to the address root\app\etc\modules\ and rename the module file for example to

You_Custom_Module.xml.old

Also look at the address root\includes\config.php so that the compilation is disabled in the file. The lines should look like:

#define('COMPILER_INCLUDE_PATH',dirname(__FILE__).DIRECTORY_SEPARATOR.'src');
#define('COMPILER_COLLECT_PATH',dirname(__FILE__).DIRECTORY_SEPARATOR.'stat');