Actionscript 3.0: keyboard events and a remote presenter

Question

I have a simple Flash movie with the following code. The idea is to move from one frame to the next or back using the arrow keys on the keyboard:

stop();

//listen for key press
stage.addEventListener(KeyboardEvent.KEY_DOWN, myKeyDown);

//if left or right arrow, go to previous or next frame
function myKeyDown(e:KeyboardEvent):void {

switch (e.keyCode) {
case Keyboard.LEFT :
prevFrame();
break;

case Keyboard.RIGHT :
nextFrame();
break;
}
}

So, this works fine, except that I need to use a Kensington Presenter to control the keyboard remotely. It should be sending a keydown command to the computer for either the right or left arrow keys, but it does not work.

It does work on a legacy Director project I have, using a similar syntax. Also works in PowerPoint.

Any thoughts would be appreciated. I'm working on a Mac, but the movie will run on Windows and Mac platforms as a compiled application.