[Dr_Bra]

пробуем со статик:

package
{
	import flash.display.*;
	import AdditionalClass;
 
	public class MainClass extends MovieClip
	{
		public static var OBJ:MovieClip;
		private var star:AdditionalClass;
 
		public function MainClass():void
		{			
			OBJ = obj_mc;
			star = obj_mc.star_mc;
		}
	}
}

package
{
	import flash.display.*;
	import flash.events.Event;
	import flash.events.MouseEvent;
 
	public class AdditionalClass extends MovieClip
	{
		public function AdditionalClass():void
		{
			this.addEventListener(Event.ADDED_TO_STAGE, init);
		}
 
		private function init(e:Event):void
		{
			MainClass.OBJ.addEventListener(MouseEvent.CLICK, stopStar);
			this.addEventListener(Event.ENTER_FRAME, moveStar);
		}
 
		private function moveStar(e:Event):void
		{
			this.rotation += 1;
		}
 
		private function stopStar(e:MouseEvent):void
		{
			this.removeEventListener(Event.ENTER_FRAME, moveStar);
		}
	}
}

выдает вот такую штуку :

TypeError: Error #1009: Cannot access a property or method of a null object reference.
	at AdditionalClass/init()
	at flash.display::Sprite/constructChildren()
	at flash.display::Sprite()
	at flash.display::MovieClip()
	at flash.display::Sprite/constructChildren()
	at flash.display::Sprite()
	at flash.display::MovieClip()
	at MainClass()