Is there a random script to jump to a point on the timeline that will function in Firefox 2.0?

I'm looking for a random script that will jump to a label along the timetime and continue to play on from that point. My client has a series of twenty banner ads in rotation, however (as we know) the Flash movie will reset to start on refresh so ads later in the sequence hardly ever get seen which the customer does not like. The the random script I found (Attached) works great in IE7, however in Firefox 2.0 (On PC only for some reason .. Mac Firefox is fine) seems to dislike it. Does anyone have any suggestions? I'd really appreciate it, as I'm very frustrated.
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function randRange(min:Number, max:Number):Number {
	var randomNum:Number = Math.round(Math.random()*(max-min))+min;   
	return randomNum; 
}     
var myFrame; 
myFrame = randRange(2,20); 
gotoAndStop(myFrame);
 
And Frames 2-20 have this action on them:
stop();
gotoAndPlay("Label");