Trouble accessing a property of an instance inside a dynamically created MC.

Question

I’m dynamically creating an instance of a movieclip, call it a game piece. This game piece has 4 frames, each with a movieclip called “base” (although one is red, one blue, one green, one yellow). When the game piece is created I set the frame to indicate player color. I’m also changing the alpha of “base” to 1.0 when it’s being dragged, 0.5 when it’s dropped.
Using the following code, everything works fine if the game piece color is set to the base in frame 1 (red). If the game piece is created and the timeline moved to a frame other than 1, I throw an error when trying to access base.alpha (this would be the second, third, and fourth instances of base in the game piece timeline). Here’s the strange part, this is only a problem when the game piece is first created and added to the display list. Once created, even after the error has been thrown, I can access the alpha of bases 2, 3, and 4 in the drag start/stop listeners. Here’s a link to the work in progress, and the relevant sections of code (shortened for brevity, t1 is the top left piece on the pallet, others just repeat the same code):
http://www.appliedcd.com/stormbringergrey/cw/CW_Combat_Sim.html
var gUnitArray:Array = new Array();
function initUnitPallet():void {
     t1.addEventListener(MouseEvent.MOUSE_DOWN,popNewUnit);
     // other pieces the same as above
     clanSelect.addEventListener(Event.CHANGE,changeClan);
function popNewUnit(e:MouseEvent):void {
     var isBase:String = e.target.name;
     var unitType:String = e.target.parent.name;
     if (isBase=="base") {
          var classRef:Class = getDefinitionByName(unitType + "master") as Class;
          var newUnit:MovieClip = new classRef();
          gUnitArray.push(newUnit);
          var newUnitIndex:uint = gUnitArray.length-1;
          this.addChild(gUnitArray[newUnitIndex]);
          gUnitArray[newUnitIndex].gotoAndPlay(clanSelect.selectedItem.data);
          // the following line is a problem if the above gotoAndPlay is anything other than frame 1
          gUnitArray[newUnitIndex].base.alpha = 1.0;
          gUnitArray[newUnitIndex].x = e.stageX;
          gUnitArray[newUnitIndex].y = e.stageY;
          gUnitArray[newUnitIndex].addEventListener(MouseEvent.MOUSE_DOWN,startUnitDrag);
          gUnitArray[newUnitIndex].addEventListener(MouseEvent.MOUSE_UP,stopUnitDrag);
          gUnitArray[newUnitIndex].startDrag();
function startUnitDrag(e:MouseEvent):void {
     e.currentTarget.base.alpha = 1.0;
     e.currentTarget.startDrag();
function stopUnitDrag(e:MouseEvent):void {
     e.currentTarget.base.alpha = 0.5;
     e.currentTarget.stopDrag();
function changeClan(e:Event):void {
     var myClanColor:String = e.target.selectedItem.data
     t1.gotoAndPlay(myClanColor);
     // other pieces the same as above

Answer 1

Thanks, pointed me in the right direction. I tried implementing a RENDER listener (see commented code below), and it worked, but unreliably. In my case the RENDER event fired before the entire frame was instantiated in about 1 out of 10 tries. I found a bunch of old posts (2007 or so) implying the RENDER event is buggy in Flash at best (apparently it has a better history in Flex). I couldn’t find more recent posts indicating better behavior, but I was unable to eliminate the residual errors in my project.
Fortunately, while reading I was reminded of the EXIT_FRAME event which seems to work perfectly (but forces me to player 10, not a big deal). Final code below along with proper Z-order control.
(BTW: I really miss the old forum's code box)
function initUnitPallet():void {
     t1.addEventListener(MouseEvent.MOUSE_DOWN,popNewUnit);
     clanSelect.addEventListener(Event.CHANGE,changeClan);
function changeClan(e:Event):void {
     var myClanColor:String = e.target.selectedItem.data
     t1.gotoAndPlay(myClanColor);
function popNewUnit(e:MouseEvent):void {
     var isBase:String = e.target.name;
     var unitType:String = e.currentTarget.name;
     if (isBase=="base") {
          var classRef:Class = getDefinitionByName(unitType + "master") as Class;
          var newUnit:MovieClip = new classRef();
          gUnitArray.push(newUnit);
          var newUnitIndex:uint = gUnitArray.length-1;
          this.addChild(gUnitArray[newUnitIndex]);
          gUnitArray[newUnitIndex].gotoAndPlay(clanSelect.selectedItem.data);
          gUnitArray[newUnitIndex].x = e.stageX;
          gUnitArray[newUnitIndex].y = e.stageY;
          gUnitArray[newUnitIndex].addEventListener(MouseEvent.MOUSE_DOWN,startUnitDrag);
          gUnitArray[newUnitIndex].addEventListener(MouseEvent.MOUSE_UP,stopUnitDrag);
          gUnitArray[newUnitIndex].addEventListener(Event.EXIT_FRAME,renderUnit);
          // gUnitArray[newUnitIndex].addEventListener(Event.RENDER,renderUnit);
          // stage.invalidate();
          gUnitArray[newUnitIndex].startDrag();
function renderUnit(e:Event):void {
     e.currentTarget.removeEventListener(Event.EXIT_FRAME,renderUnit);
     // e.currentTarget.removeEventListener(Event.RENDER,renderUnit);
     e.currentTarget.base.alpha = 1.0;
function startUnitDrag(e:MouseEvent):void {
     if(this.numChildren > 1){
          e.currentTarget.parent.setChildIndex(e.currentTarget,this.numChildren-1);
     e.currentTarget.base.alpha = 1.0;
     e.currentTarget.startDrag();
function stopUnitDrag(e:MouseEvent):void {
     e.currentTarget.base.alpha = 0.5;
     e.currentTarget.stopDrag();