AS3: help a newbie (game hit test issue)

programming flash
1

Getting an error: #2007 Parameter hitTestObject must be non-null

Essentially the game is not registering a hit. See my Bomb.as file below

Thanks for any help!

package {

import flash.display.*;
import flash.events.*;
import Icons;

public class Bomb extends MovieClip {
	
	// NEW CODE
	public var speed:Number = 10;
	public var rootTimeline:MovieClip;
	
	
	public function Bomb(parentTimeline:MovieClip, parentIcons:Icons)
	{
		// NEW CODE
		rootTimeline = parentTimeline;
		
		trace(parentIcons.x);
		
		this.x = parentIcons.x;
		this.y = parentIcons.y;
		addEventListener(Event.ENTER_FRAME, moveBomb);
	}
	
	public function moveBomb(e:Event)
	{
		
		// NEW CODE dropping the bomb and some time is added - same idea as Pointer
		this.y = this.y + speed;
		
		if(this.y > 500){
			this.removeEventListener(Event.ENTER_FRAME, moveBomb);
		}[COLOR="Red"]else if(this.hitTestObject(rootTimeline.playermouse) && rootTimeline.playermouse.currentFrame == 1){
			rootTimeline.registerHit();
			this.y = 510;[/COLOR]
		}
	}

}

}

// had this 1: }else if(this.hitTestObject(rootTimeline.playermouse) && rootTimeline.playermouse.currentFrame == 1){

// had this 2: }else if(rootTimeline.playermouse && this.hitTestObject(rootTimeline.playermouse) && rootTimeline.playermouse.currentFrame == 10){