Tweeners' great, but I came across one little problem the other day: when I tried to remove an externally loaded swf from the stage while it was mid-animation, Tweener could bring the whole Flash movie to a halt with the error '256 levels of recursion were exceeded in one action list'.
Obviously that's bad - because this particular error completely stops the flash player with no warning to the end user. And the fact that external content - which I have no control over - can cause this is doubly bad.
All is not lost however, because Tweener has a useful little function: Tweener.removeAllTweens(); ok, so it can interfere with everything on your flash movie as well, but at least it's stopping the recursion errors.
So, if you try to remove a loaded swf file with .removeMovieClip(), you might find that it's using Tweener. And if so, call Tweener.removeAllTweens() before you call .removeMovieClip() and you'll be fine. Phew! case closed.