ActionScript 3.0 :: Getting Error 1009 With Creating Transitioning Pages

I am a college student who has to create an assignment involving an Apple interface, with transitional pages. The problem is that with the actionscript on the first frame, nothing starts up. All i get is this error and nothing else, no line errors.
TypeError: Error #1009: Cannot access a property or method of a null object reference.
at flash_project_two_fla::MainTimeline/frame1()

Here is the actionscript
//declaring variable
var page = "touch";
//event listeners
touchBtn.addEventListener(MouseEvent.MOUSE_DOWN,goTouch);
nanoBtn.addEventListener(MouseEvent.MOUSE_DOWN,goNano);
[Code] .....

Here is the FLA. it's like 300kb. [URL]