Error #1009 when I add a button to the stage

Hi there -
Argh.I have a timeline project. Each “date” aka button when clicked advances to its respective named frame. It works fine until I have a section of the timeline with more than one “entry”. I use the same naming process as i did for the main sections using a “next >” button and coding it the same way I coded the main buttons but it doesn’t work. I get:
[COLOR=Red]
Type Error: Error #1009. Cannot access a property or method fo a null object reference at Timeline_Sce3_fla::MainTimeline/frame1()[/COLOR]

[COLOR=Black]My fla is posted here : [/COLOR]http://www.iser.uaa.alaska.edu/test/Flash/Timeline_Sce3.fla

I’ve dragged an instance of the bttn_next onto the stage, given it an instance name, inserted a keyframe into the layer and named the layer to advance to. I know there’s something wrong with this button - could this be a flow or inheritance problem? i’ve commented out the line that throws the error (starts with //btn1974b…). the code reads:

stop();

b1971.addEventListener(MouseEvent.CLICK,clickSection);
b1973.addEventListener(MouseEvent.CLICK,clickSection);
b1974.addEventListener(MouseEvent.CLICK,clickSection);
//btn1974b.addEventListener(MouseEvent.CLICK,clickSection);
b1976.addEventListener(MouseEvent.CLICK,clickSection);
b1977.addEventListener(MouseEvent.CLICK,clickSection);
b1980.addEventListener(MouseEvent.CLICK,clickSection);
b1982.addEventListener(MouseEvent.CLICK,clickSection);
b1985.addEventListener(MouseEvent.CLICK,clickSection);
b1986.addEventListener(MouseEvent.CLICK,clickSection);
b1987.addEventListener(MouseEvent.CLICK,clickSection);
b1989.addEventListener(MouseEvent.CLICK,clickSection);
b1990.addEventListener(MouseEvent.CLICK,clickSection);
b2005.addEventListener(MouseEvent.CLICK,clickSection);
b2006.addEventListener(MouseEvent.CLICK,clickSection);
b2008.addEventListener(MouseEvent.CLICK,clickSection);
b2009.addEventListener(MouseEvent.CLICK,clickSection);

//handle events for buttons

function clickSection(evtObj:MouseEvent) {
//trace action show’s what’s happening in output window
trace(""+evtObj.target.name+“button was clicked!”);
gotoAndStop(evtObj.target.name);

}

any help is GREATLY appreciated.

thanks