ActionScript 3.0 :: Navigation Error

I have created a basic site with 7-8 pages which are each given their own label on the timeline. I have created a function called navigate which as the name suggests navigates to each page. This code works and does navigate to all pages within the site. But on only one page ( the last one on the timeline ) I get the error " TypeError: Error #1009: Cannot access a property or method of a null object reference. at index_fla::MainTimeline/navigate() " I will also post the navigate function which is

// create function to react to the navigation listeners function navigate(evtObj:MouseEvent){//trace to show that button is identified when clicked trace("the "+evtObj.target.name+" button was clicked!") //go to the section clicked on gotoAndStop(evtObj.target.name) //stop the video playback videos_mc.chili_player.stop();
} I have double checked all labels and instance names and the grammar and am pretty sure it is nothing to do with that.