I'm getting the following error when trying to install v1.4.3 on a WAMP 2.5 development server. Apache 2.4.9 PHP 5.5.12 MySQL 5.6.17 Everything checks out fine then I click the Begin Installation button and it creates the tables and then I get this error. Error invalid_class_x Any ideas why this might be happening? I have uninstalled and re-installed WAMP server and get the same result. I have also tried EasyPHP and XAMPP servers with the same result.