ActionScript 2.0 :: Flash File Reading An External Text File For The Content?

I turn to you for help, dear sweet Kirupa Forumites. First, let me explain the problem: I have a flash file reading an external text file for the content. Everything works perfectly for nearly everyone - you click a menu button, and the content text comes up fine. However, a couple of people have found that the text shows up as "undefined". I have checked the player versions of the people where it doesn't work, and it is the same as for those where it does work, so that ain't the problem.

I don't understand why it works perfectly for nearly everyone, but a small number of people have this "undefined" text problem. It seems to be a problem with loading the external text file, but I don't know why. I have a main flash movie, and load the text in the first frame, using the following:

var my_content = new LoadVars();
my_content.load("content.txt");
my_content.onLoad = function(success){
if (success){

[Code]...

I then have a couple of dynamic text boxes in the main movie - one called ErrorText (for displaying an error message to the user) and one called ContentText (for displaying the content). I use an external menu swf which jumps to a specific frame in the main movie, depending on which button is clicked. Actionscript on the main movie frame for the first button does the following, with the other frames similarly configured:

ContentText.htmlText = my_content.content1;
stop();

My external text file is properly configured (content1=blah blah&content2=other blah blah) etc.

Does anyone have any advice on how I can solve this particular weird problem??