Bouncing Balls, help needed

Am experimenting with Flash and i would appercaite if someone can help me out with it. Here is scenario …

  1. A row of balls, let say 4 drop from the sky in order of left to right, with about a second between them. (so the 1st ball drops, one second later the 2nd drops and so on)

  2. the balls hit the ground in the same order they dropped in …

  3. … and bounce back to their original positions

  4. and loops smoothly to repeat the above steps.

As you can see from the links below (swf and fla files), after the first loop the order of the balls gets messed up. i been trying for days to figure out the problem but i make it worse. am not sure whether i should be including actionscripting or not.

http://www.brunel.ac.uk/~ee03aas/sequence%20boucing%20balls2.swf
http://www.brunel.ac.uk/~ee03aas/[color=#003366]sequence%20boucing%20balls2.fla[/color]