Help needed with leaving trails

Hi everyone

I am new to the whole actionscript thing and have been learning as I go along.

I am trying to make a animated ball that goes round a path, but that leaves trails behind it.

I have managed to get most of it right, but after the animation plays for a few seconds it seems to slow down badly. I think it is not removing the duplicate movie clips!

Could someone have a look at the file and see if they can find a solution for me?

Your help would be greatly appreciated