setMask targets doesnt work

1

Hi before i go onto the problem here is the code of what im trying to do.

on (release) {
    _root.playBox._rotation = this._rotation-90;
    if (_root.playBox._rotation>0) {
        _root.playBox._rotation -= 180;
    }
    this.duplicateMovieClip("mLine"+_root.mLineInt, _root.mLineInt);
    name = "mLine"+_root.mLineInt;
    mc = _root[name];
    mc._alpha = 50;
    mc._x = this._x;
    mc._y = this._y;
    _root.mLineInt++;
    mc.setMask(_root.mA);
    _root.playBox.movie.play();
}

This code is set in a movie clip. When i release it, a duplicate of the clip is made and i want to set the mask of the clip to mA. When i do it the first time the mask works however when i click it subsequently, the first duplicate clip will no longer be masked and the whole movie clip will be shown.

Any ideas why?

Thanks in adv!