Class 'C_PhpChartX' not found
Open conf.php, and make sure the first line is
define('SCRIPTPATH', str_replace(str_replace('\\', '/', realpath($_SERVER['DOCUMENT_ROOT'])),'', str_replace('\\', '/',dirname(__FILE__))).'/');
This line parses the relative path to the phpChart library. Occasionally, it has trouble find the path when virtual hosts are used. In that case, you can always manually set the path, such as:
define('SCRIPTPATH', '/www/localhost/my-site/phpChart/')