Problems with fading grid!

I have some newbie problems following the Fading grid tutorial.
I have followed the steps exactly but get this error loading the movie;

A script in this movie is causing flash player to run slowly. If it continious to run, your computer may become unresponcible. Do you want to abort this script yes, no?

Ofcourse i dont want to abort it! What have i done wrong? I just copied and pasted the script as i was told?

Thanks!