Thanx for the reply... but thats not it I'm afraid.
If you look at the Event class it declares a lot of constants but the URLLoader.addEventlistener(type:String, ...) method actually somewhere declares which one of those are valid input.
Have a look in the as3 documentation for the URLLoader class. Scroll down to the table called "Events" (thats the third one). As you can see, those are a subset of a lot of static constants declared in a lot of different classes and among the the Event class.
Whats also interesting is that two of the "valid events" is inherited. Wats also interesting is that the "valid events" is not connected to the method addEventListener(...) since that one also is inherited. It seems to be some sort of declaration on its own... And I want to know how to do that NOW!
As you can see from the attached image, The super class of URLLoader, EventDispatcher has only declared two events.