Making Main Images Links in Photo Gallery

Hello.

I've made an image gallery and it works great. What I want to do is make the main image a link to a certain part of the site. The first link works great, but then I get: TypeError: Error #1009: Cannot access a property or method of a null object reference.
at Rockit_Front_Ad_fla::MainTimeline/frame1().

Basically, I made an invisible button on each main image for the link.

Can anyone help? Just want the links to work and can't get it. Any help is greatly appreciated. My AS3 is below:

Mike

stop();

Button1.addEventListener(MouseEvent.CLICK,showPic1);
Button2.addEventListener(MouseEvent.CLICK,showPic2);
Button3.addEventListener(MouseEvent.CLICK,showPic3);
Button4.addEventListener(MouseEvent.CLICK,showPic4);
Button5.addEventListener(MouseEvent.CLICK,showPic5);
Button6.addEventListener(MouseEvent.CLICK,showPic6);
Button7.addEventListener(MouseEvent.CLICK,showPic7);

IMG1.addEventListener(MouseEvent.CLICK,IMG1ClickHandler);
IMG2.addEventListener(MouseEvent.CLICK,IMG2ClickHandler);
IMG3.addEventListener(MouseEvent.CLICK,IMG3ClickHandler);
IMG4.addEventListener(MouseEvent.CLICK,IMG4ClickHandler);
IMG5.addEventListener(MouseEvent.CLICK,IMG5ClickHandler);
IMG6.addEventListener(MouseEvent.CLICK,IMG6ClickHandler);
IMG7.addEventListener(MouseEvent.CLICK,IMG7ClickHandler);

function showPic1(Event:MouseEvent):void{
gotoAndStop("Pic1");
}
function IMG1ClickHandler(Event:MouseEvent):void{
navigateToURL(new URLRequest("http://www.rockitmusic.com/products.asp?cat=31"));
}
function showPic2(Event:MouseEvent):void{
gotoAndStop("Pic2");
}
function IMG2ClickHandler(Event:MouseEvent):void{
navigateToURL(new URLRequest("http://www.rockitmusic.com/proddetail.asp?prod=BOOGIETA15"));
}

function showPic3(Event:MouseEvent):void{
gotoAndStop("Pic3");
}
function IMG3ClickHandler(Event:MouseEvent):void{
navigateToURL(new URLRequest("http://www.rockitmusic.com/products.asp?cat=61"));
}

function showPic4(Event:MouseEvent):void{
gotoAndStop("Pic4");
}
function IMG4ClickHandler(Event:MouseEvent):void{
navigateToURL(new URLRequest("http://www.rockitmusic.com/proddetail.asp?prod=MM25THANN"));
}

function showPic5(Event:MouseEvent):void{
gotoAndStop("Pic5");
}
function IMG5ClickHandler(Event:MouseEvent):void{
navigateToURL(new URLRequest("http://www.rockitmusic.com/products.asp?cat=14"));
}

function showPic6(Event:MouseEvent):void{
gotoAndStop("Pic6");
}
function IMG6ClickHandler(Event:MouseEvent):void{
navigateToURL(new URLRequest("http://www.rockitmusic.com/products.asp?cat=27"));
}

function showPic7(Event:MouseEvent):void{
gotoAndStop("Pic7");
}
function IMG7ClickHandler(Event:MouseEvent):void{
navigateToURL(new URLRequest("http://www.rockitmusic.com/products.asp?cat=49"));
}