Script non funzionante se non in Flash 6

[zeropunto]

Qualcuno sa dirmi perchè questo script funziona solo se pubblicato per Flash6 e AS 1 o 2 e invece non va se pubblicato per Flash 7 AS1 o 2?

maskNum = 13;
ratio = 0.14999999999999999;
friction = 0.59999999999999998;
mask._visible = 0;
foto_mc._visible = 0;
stageWidth = 800;
StartY = 450;
gap = 30;
count = 4;
j = 1;
k = 1;
i = 1;
while (i <= maskNum) {
	attachMovie("mask", ("mask" + i), (i + 1889));
	mc = this[("mask" + i)];
	mc._x = _root.stageWidth / 7;
	mc._y = mc.posY = -mc._height;
	mc.onEnterFrame = function() {
		if (this.active) {
			this.nextFrame();
		} else {
			this.prevFrame();
		}
		this.next_pos = (this.posY - this._y) * _root.ratio + this.next_pos * _root.friction;
		this._y +=  this.next_pos;
		if (this.posY <= this._y && this.done) {
			this.active = true;
		}
	};
	foto_mc.duplicateMovieClip(("foto_mc" + i), (i + 9908));
	this[("foto_mc" + i)].setMask(mc);
	i++;
}
_root.onEnterFrame = function() {
	if ((j % count) == 0) {
		this[("mask" + k)].posY = this.StartY - this.gap * (k - 1);
		this[("mask" + k)].done = true;
		k++;
	}
	j++;
	if (k > maskNum) {
		this.onEnterFrame = null;
	}
};
txt.onEnterFrame = function() {
	if (_root[("mask" + _root.maskNum)].active) {
		this.gotoAndPlay(2);
		this._visible = 1;
		this.onEnterFrame = null;
	}
};
txt.swapDepths(10000);
txt.stop();
txt._visible = 0;