ActionScript 3.0 :: Getting Error 1009 When Navigating Through Tested Files

I am new to flash. I am experiencing random (at least to me) errors (#1009) while navigating through my tested file. I can't reproduce them everytime. It only happens sometimes. Usually they occur after I have clicked back and forth between different pages (frames). Sometimes the error shows up once, and the file moves on as if nothing bad has happened. Sometimes the error continuosly displays, which really slows down the test.

One example of such:
TypeError: Error #1009: Cannot access a property or method of a null object reference.
at About28_fla::MainTimeline/clickResumeFromAbout()

The general structure of my file is this: I have pages laid out on separate frames with movieclips embedded within each other on the frames. Navigational movieclip buttons remain on essentially every frame. Three of them are: 'About', 'Contact', and 'Resume'. I wrote Listeners for each frame that go from that frame to any of the others. For example, to get from my 'Resume' frame from the 'About' frame, I wrote a Listener called 'clickResumeFromAbout', which is what the above error refers to.

The code in context:
mResumeGlow.addEventListener(MouseEvent.CLICK, clickResumeFromAbout);
function clickResumeFromAbout(e:MouseEvent):void {
mBoxAbout.gotoAndPlay(mBoxAbout.totalFrames-mBoxAbout.currentFrame);
mBoxAbout.addEventListener(Event.ENTER_FRAME, enterResume);
function enterResume(event:Event):void {
if (mBoxAbout.currentFrame == 150){
mBoxAbout.stop();
mBoxAbout.removeEventListener(Event.ENTER_FRAME, enterResume);
gotoAndStop("Resume");
}}}

However, the error above occurs when I click 'Resume' from 'Contact' (not from 'About' as the error states). It only occurs after I've been flipping between frames for a bit (I'm assuming I've clicked 'About' at some point).