External swf question...

Question

Hey all
I found this code for loading external swfs and playing them in succession.
It works when I use the external swfs that come with the code, but not when I try to use any other external swfs.
I can't figure out why - does anything seem obvious (the clip swfs are here http://www.flashandmath.com/intermediate/externalclips/clip0.swf http://www.flashandmath.com/intermediate/externalclips/clip1.swf http://www.flashandmath.com/intermediate/externalclips/clip2.swf ):
// Array of external clips to use. Variable index refers to next clip to be displayed.
var clips:Array = ["clip0.swf", "clip1.swf", "clip2.swf"];
var index:int = 0;
// Stuff to load swf files
var thisLoader:Loader = new Loader();
thisLoader.contentLoaderInfo.addEventListener(Event.INIT, doneLoading);
//loader.contentLoaderInfo.addEventListener(Event.COMPLETE, dataOnLoad);
var thisMC:MovieClip = new MovieClip();
stage.addChild(thisMC);            // Add empty MC initially so the nextClip function can be generic
// Removes old MC and gets the next one, waiting until when it has initialized beore adding it to the stage
function nextClip():void {
    thisLoader.load(new URLRequest(clips[index]));
// Tell AS that the loaded file is a movie clip and add it to the stage.
function doneLoading(e:Event):void {
stage.removeChild(thisMC);
thisMC = MovieClip(thisLoader.content);
thisLoader.unload();
thisMC.addEventListener(Event.ENTER_FRAME, runOnce);
stage.addChild(thisMC);
thisMC.gotoAndPlay(1);
// When thisMC has finished, play the next clip.
function runOnce(e:Event):void {
if (thisMC.currentFrame == thisMC.totalFrames) {
thisMC.removeEventListener(Event.ENTER_FRAME, runOnce);
index = (index + 1)%(clips.length);
nextClip();
// Call the nextClip function initially to get the ball rolling
nextClip();
Thanks for taking a look guys.
Shaun

Answer 1

One of the swfs returns:
TypeError: Error #1034: Type Coercion failed: cannot convert flash.display::AVM1Movie@26f9b3a1 to flash.display.MovieClip.
    at alt2_fla::MainTimeline/doneLoading()
(I'm pretty sure it's an AS3 swf)
The other, which I had just built using AS3, returns:
TypeError: Error #1009: Cannot access a property or method of a null object reference.
    at fl.rsl::RSLPreloader/loadContent()
    at _001_fla::MainTimeline__Preloader__/frame2()
Error: Error #2099: The loading object is not sufficiently loaded to provide this information.
    at flash.display::LoaderInfo/get width()
    at loader_animation_fla::MainTimeline/frame1()
Error: Error #2099: The loading object is not sufficiently loaded to provide this information.
    at flash.display::LoaderInfo/get width()
    at loader_animation_fla::MainTimeline/frame1()
TypeError: Error #1009: Cannot access a property or method of a null object reference.
    at fl.rsl::RSLPreloader/loadContent()
    at _001_fla::MainTimeline__Preloader__/frame2()