Error when creating new levels v.1.3.3

[Hwona]

Sorry to be a bugger, but I'm getting this error when I try to create new adoptable levels:
Fatal error: Uncaught exception 'Exception' with message 'Fatal Error: Class Registry either does not exist, or has its include path misconfigured!' in /home/wallie987/public_html/classes/class_loader.php:60 Stack trace: #0 [internal function]: Loader->load('Registry') #1 /home/wallie987/public_html/classes/class_initializer.php(103): spl_autoload_call('Registry') #2 /home/wallie987/public_html/classes/class_initializer.php(42): Initializer->initialize() #3 /home/wallie987/public_html/index.php(81): Initializer->__construct() #4 /home/wallie987/public_html/index.php(90): IndexController::main() #5 {main} thrown in /home/wallie987/public_html/classes/class_loader.php on line 60
Does anyone know how to fix this? :3