[MC became a mask] Is it a flash MX bug?

Hi there!

I currently working on a web project and try to load some character with clothes into my flash MX movie 6.0 but turn out ran into trouble.
So pls kindly drop me a comment or something. Thanks in advance.

The Movie structure is like below:

STAGE
|_________MC#1 (depth=1400)
|
|
|_________MC#2 (depth=1500)
|
|
|_________MC#3 (depth=1600)
|
|
|_________MC#4 (depth=1700)
|
|
|_________MC#5 (depth=1800)
|
|
|_________MC#6 (depth=1900)

All the MC above are created by attachMovie.
And each of the six MC contained 2 child MC(depth=11, 18), and the child MC contained a .swf file by loadMovie();

However, when I test the movie, part of MC#6 become MASK of #MC1
The screenshot is something like this:

And I heard if 10 layers (altho in different MC timeline) stacked together can be a mask effect bug.
URL: http://www.flashkit.com/movies/Effects/Masking/Scriptab-Justin_E-1448/index.php
So is it same stuff?

Regards,
Camus

=======Some codes=======

Character.prototype.update = function(){
Obj=eval(this.$name);
localNode = Obj.$char_XML.childNodes[0];
for (i=0; i<localNode.childNodes.length; i++){
mcLevel = int(localNode.childNodes*.attributes.level);
mcDescription = localNode.childNodes*.attributes.description;
mcID = localNode.childNodes*.attributes.id;

Obj.createEmptyMovieClip(mcLevel, mcLevel);
ElementObj = eval(Obj+'.'+mcLevel);
if (mcID!=""){
	fileName = "virtualimage/"+mcLevel+mcDescription+"/"+mcID+".swf";
	ElementObj.loadMovie(fileName);
	ElementLayer= ElementObj.getDepth()
	with (ElementObj){
		ParentLayer = _parent.getDepth();
	}
}

}
}

makeCharacter = function(Name, Expression, Sex, Level){
this.attachMovie(“CharacterHolder”, Name, Level).init(Expression, Sex, Level);
}

Zip file: http://www.magusequine.com/lawfui/Query.zip