Код AS3:
var BirthInfoWindow:TitleWindow = TitleWindow(PopUpManager.createPopUp(this, UserBirth_form, true));
Вместо TitleWindow, нужно использовать UserBirth_form:
Код AS3:
var BirthInfoWindow:UserBirth_form = UserBirth_form(PopUpManager.createPopUp(this, UserBirth_form, true));