Tween Class Problem?

AS 2.0

Im not sure why this isnt working… I want the MC to move up then down using one function… but it glitches and jumps all over, not sure why. Any Ideas???

import mx.transitions.Tween;
import mx.transitions.easing.*;
jump = function () {
 var yMove:Tween = new Tween(blob_mc, "_y", Elastic.easeOut, 400, 300, 2, true);
 yMove.onMotionFinished = function() {
  yMove.continueTo(400,2);
 };
};

Works for me.

If i try to play it more than once it jumps randomly up and down…

Here is the File

If you call the function before the last tween has finished then the new one will interfere with it since they are both trying to tween the same property of the same object.