Randomly stopping ActionScript 3.0 Tweens, anyone?

Your animation hangs randomly and you can't reproduce the bug? — One possible cause for that problem is the scope of the tween object:

Any local variable will only be referenced until the function in which it was defined returns (that's propably a few ms). Your tween, however, takes a lot longer to finish. If the garbage collector (GC) decides to clean up during the time in which the tween is unreferenced it will remove the object and thereby stop the animation.