[Vektor]

var i:Number = 0;
var mcName:MovieClip;
this.onMouseDown = function() {
	if (img.hitTest(_xmouse, _ymouse)) {
		mcName = this.attachMovie("MC", "name"+i, i, {_x:_xmouse, _y:_ymouse});
		i++;
	}
	this.mcName.onRollOver = function() {//Это работает
		trace("Hellow, world!");
	};
};

И так можно.

var i:Number = 0;
var mcName:MovieClip;
img.onPress = function() {
	mcName = attachMovie("MC", "name"+i, i, {_x:_xmouse, _y:_ymouse});
	i++;
	mcName.onRollOver = function() {
		trace("Hellow, world!");
	};
         //Если, нужно удалять мувик.
         mcName.onRollOut = function() {
		mcName.removeMovieClip();
	};
};