ActionScript 3.0 :: Getting Error 2007 When Loading SWF Files

I am just learning ActionScript3 and am trying to create a fla file that loads 3 external SWF. I have already created and saved the 3 SWFs and they are all saved in the same folder. I have given them the names "A.swf" "B.swf" and "C.swf" so they are easy for me to keep track of. I created the actionscript below and placed it in the first frame of my parent file which is saved in the same folder.

import flash.display.MovieClip;
import flash.display.Loader;
var swfContainer:MovieClip;
var swfLoader:Loader = new Loader();
[Code] .....

When I insert the filename in the URLRequest statement "A.swf" and test the movie it works loading the swf movie and playing it. When I swap either the "B.swf" or "C.swf" file names in the place of the "A.swf" it doesn't work. I end up with no swf file loaded or played on the stage. I also get the following error statement. But I am confused because it is in the Output Tab not the Error Tab which does not report any errors.

TypeError: Error #2007: Parameter child must be non-null.
at flash.display:isplayObjectContainer/addChild()
at SWFadMovieClips_fla::MainTimeline/loaderCompleteHandler()

Although I shouldn't be too surprised as it is written for use with CS.3 and I am using CS.5. Eventually my goal is to create one fla file which loads and plays in succession the three separate swf files in one package.