Whatever it is, it is in the file you are working on, assuming you are working on the file that creates home.swf. You can likely confirm this yourself by simulating download in the Flash Player... I could. So there's a chance that your file has some preloader animation built into it to either act as an actual preloader or to fool visitors into thinking it is. If you search the library you might find the animation.
You should visit gotoAndLearn.com and consider the preloader tutorial there... http://www.gotoandlearn.com/play.php?id=85
As always, thanks Ned. That was a great tutorial and it worked much better than what i tried.
Wierd. I never could determine what was making that circle animation. Once I removed the frames that contained my preloader assets and code, the problem went away. I guess that's another good reason to use the method outlined in the tutorial.
You're welcome Scott