Preloader not counting

Can someone tell me why this very simple preloader is not counting? It´s stuck on 1% (or whatever), then eventually the content of the next scene fills the screen. If you can´t open the attached file here´s the plan:

There are 3 scenes. Scene 2 and 3 are just filled with images, or that´s the idea at least.

Scene 1 is called “Preloader”. It contains one layer(“actions”) with two frames. The first frame has the following actionscript:

a = getBytesLoaded();
b = getBytesTotal();
c = Math.ceil((a/b)*100)+"%";
if(a == b) {
nextScene();
}

The second frame has the following action:

gotoAndPlay(1);

In the first frame of the actions layer, on the stage, there is a dynamic textbox with the variable “_root.c”(no quotations).

That´s all.