Need to fix Error 1009 for very simple task!

Question

Hi to all,
I'm learning AS3 for the first time so that I can make a game, but I'm stuck on the most basic of tasks!
What I want to do is be able to click on a button to take me to the next frame of the main timeline, which I've called "gameboard". The button is called "storymode".
In the first frame of the main timeline, I have a movie clip that runs a short animation before the menu appears. My button that I want to click on is nested in this movie clip.
This is the code I'm using on frame 95 of the movie clip (exactly where the button appears):
stop();
storymode.addEventListener(MouseEvent.MOUSE_UP, gotoGame);
function gotoGame(evt:MouseEvent):void {
evt.target.parent.gotoAndStop("gameboard");
...but it just gives me Error 1009 every time and won't work!
I've read a few other forums for help on this error already and tried a few potential solutions, but nothing works - so I'm asking my own question! Also, I ran the debugging tool in Flash, and it tells me the error is specifically on Line 3 (beginning with the word 'storymode'). I've made sure that everything has a name, and double and triple-checked that I'm referring to the right names in the right places, so "storymode" does indeed refer to my button!
One cause I read about was that the button may not have been loaded yet, but I've made sure that the code is on the same frame as the button. It appears in the exported file and changes colour when hovered over like a functional button, so it's definitely loaded! It just doesn't work when clicked! What could the problem be?!
I am utterly bewildered by this and desperately need help, otherwise I will never be able to progress to more difficult tasks!

Answer 1

Kglad, I did as you suggested, and that gives me not only another error (1120: Access of undefined property titlemenu (that's the name of the movieclip)), but it also negates all the "stop" commands I've put in the timeline actions, resulting in the export flickering uncontrollably between the first and second frames on the main timeline.
I had this problem before I had the 1009 error, and managed to fix it on my own. Back then, it was Error 1061, and was caused by me using the wrong target in my code. I had:
this.parent.gotoAndStop("gameboard")
instead of
evt.target.parent.gotoAndStop("gameboard")
...and changing it to the latter fixed Error 1061. However, this error 1120 causes the same problem again, so it's a targeting issue I'm not very willing to change, I think.
I've tried about a dozen different targeting options as well, and none of them solve Error 1009.