Pre-loading sound displays wrong bytesTotal

programming flash
1

I’m working on a game for school and set up a pre-loader which waits for the main movie to finish loading. We have some background music in external files which I also wanted to pre-load. I set up the pre-loader to start pre-loading the first song out of 3 after the main movie has finished loading. However, for all 3 MP3s, the bytesLoaded and bytesTotal show up as the exact same value. I’m not sure if I’ve done anything wrong or not. The following function is what updates my pre-loader’s progress bar:

        private function updateProgressBar(bytesLoaded:Number, bytesTotal:Number) {
            var KBbytesLoaded:int = Math.round(bytesLoaded / 1024);
            var KBbytesTotal:int = Math.round(bytesTotal / 1024);
            var ratio:Number = bytesLoaded / bytesTotal;
            kbLoaded.text = KBbytesLoaded + " / " + KBbytesTotal + " KB";
            percentLoaded.text = Math.round(ratio * 100) + "%";
            preloadBar.width = ratio * 200;
        }

This works fine with the main movie’s pre-loading. An example of how I’m trying to load the MP3s:

                // create a URL request for the MP3
                var request:URLRequest = new URLRequest("bgm/bgm" + currentBgmusicNumber + ".mp3");
                // create the new sound, set up event handlers, and load the sound
                var sound:Sound = new Sound();
                sound.addEventListener(ProgressEvent.PROGRESS, onProgress);
                sound.addEventListener(Event.COMPLETE, onComplete);
                sound.load(request);

Any help would be appreciated, as I’m stumped as to why the bytesLoaded and bytesTotal would be exactly the same. You can see it failing in action at http://kirby.cyberbotx.com/SpaceshipSOCKS.html

Edit: The bytesLoaded and bytesTotal display only show as the same when the SWF is loaded in Firefox, in IE, the bytesTotal is 0 and the percent shows up as Infinity%.