Problem importing text data into dynamic text field

Head slowly banging into wall on this one. I’ve done it before but for some reason I’m missing something here.

Particulars – I’ve got a flash movie with a menu that jumps to a particular frame to load a page. On that frame, there is a movie clip (instance name: scrollbox_frame), and in that movie clip there is a four-layer animation. One of the layers is not animated but contains a dynamic text box (instance name: about_frame), with multi-line and HTML turned on, and a variable name of “aboutus”. This is the code that is triggered by the menu button on the root of the flash movie:

myVariables = new LoadVars();
myVariables.load("text1.txt");
myVariables.onLoad = function(success){
if(success){ 
about_frame.text=myVariables.aboutus;
}
}

and this the text1.txt document:

aboutus=ABOUT US <br>blah blah blah

It’s not working, and I’ve tried seemingly dozens of permutations. What am I missing? Anybody?