codice:
import mx.transitions.*;
import mx.transitions.easing.Regular;
import mx.transitions.easing.Strong;
import mx.transitions.easing.Back;
import mx.transitions.easing.Elastic;
import mx.transitions.easing.Bounce;
import mx.transitions.easing.None;

var ___TWEEN___:Tween = new Tween(_root.___MC___, "_x", Regular.easeIn, 0, 200, 10, false);
Continua a non funzionare, ho anche ricontrollato di avere instanziato correttamente il movie clip.