Maniac, that message means that the updater is seeing something different in your current installation than what it is expecting. This is usually caused by either a disk error or a virus. I'd recommend doing a disk scan followed by a virus scan. After that, you'll need to reinstall AH. Hopefully, you still have the downloads on your box.
Horn, did you just start getting that message after the update or have you been doing anything with DirectX or sound drivers?