My preloader dont work right all the time!! help

[maydays]

Hi
I have this script for a preloader that i used on 2 pages and worked just fine but on my last page the preloading starts working when the loading is at 50% until then its all white.

code:

---

stop();

myInterval = setInterval(preloader,10);

function preloader() {

    if (getBytesLoaded() >= getBytesTotal()) {

        play();

        clearInterval(myInterval);

    }

    progressBar._xscale = (getBytesLoaded()/getBytesTotal())*100;

}

---

Can anyone tell me whats the problem?, i thing is my page not the preloading since it works fine on 2 pages.

Thank you very much.