[eluser]Mark van der Walle[/eluser]
I just got an e-mail from someone asking for help with this. I did not realise alot of people are using this. I can at least point to a significant flaw in my code. It is as Bluemill posted, when a non-existing method is called on an existing controller.
The problem is that the controller IS the Codeigniter object and in this case a new controller is created without all the models, libraries and other stuff you already should have in the controller. My code was written to get 404's working without hacking the CI core.
The only way to have all your libs and models is to copy them over. Mostly the only thing I needed in my errorhandler was a database object. Perhaps Ill look into modifying the code a bit to allow for all libraries and models to be available.