Credo sia qualche parentesi mancata...
Ma a me non da nessun errore:
codice:onClipEvent(enterFrame){ if(_parent.avanti){ if (_parent._currentframe>(_parent._totalframes/2)) { gotoAndPlay (_parent._totalframes-_parent._currentframe); } else { _parent.play (); } } else { if (_parent._currentframe<(_parent._totalframes/2)) { gotoAndPlay (_parent._totalframes-_parent._currentframe); } else { _parent.play (); } } }