Preloader making flash player slow

I am trying the this script for the preloader

bytes_loaded = Math.round(_root.getBytesLoaded());
bytes_total = Math.round(_root.getBytesTotal());
getPercent = bytes_loaded/bytes_total;
_root.loadBar._width = getPercent150;
_root.loadBar2._width = getPercent
150;
_root.loadText = Math.round(getPercent*100)+"%";
if (bytes_loaded == bytes_total) {
_root.gotoAndPlay(3);
}
else
_root.gotoAndPlay(1);

at the first frame, and it is running with 620 kb swf but with the 407kb swf it is not loading the frames and prompting with the message, "the script making the flash player7 slow, and this can cause computer unresponsive. Please help me, it is urgent.