Strange Display Results in Tile Map

//---------------------------------------------------------------------------------------------
// Torque 2D. 
// Copyright (C) GarageGames.com, Inc.
//---------------------------------------------------------------------------------------------

//---------------------------------------------------------------------------------------------
// startGame
// All game logic should be set up here. This will be called by the level builder when you
// select "Run Game" or by the startup process of your game to load the first level.
//---------------------------------------------------------------------------------------------
function startGame(%level)
{
   // Set The GUI.
   Canvas.setContent(mainScreenGui);
   Canvas.setCursor(DefaultCursor);
   
   moveMap.push();
   sceneWindow2D.loadLevel(%level);
   
   new ScriptClass(gridObj);
   
   $gridObj.init();
}

//---------------------------------------------------------------------------------------------
// endGame
// Game cleanup should be done here.
//---------------------------------------------------------------------------------------------
function endGame()
{
   sceneWindow2D.endLevel();
   moveMap.pop();
}

function gridObj::onAdd(%this)
{
   $gridObj = %this;   
}


function gridObj::init(%this)
{
   // Make the checkerboard
   %this.tileMap = new t2dTileMap() { scenegraph = t2dScene; };

   // 8x8 tile layer, each tile is 64x64
	  %this.gridLayer = %this.tileMap.createTileLayer( "8 8 64 64" );
	  
	  
   // The board needs to be centered
   %this.gridLayer.setPosition("0 0");
   
   // The board itself is 512 (8 * 64)
	  %this.gridLayer.setSize( "512 512" );
	  
	  %this.gems = new SimSet();
	  
   
   // This is render-layer 30, which is way to the back, it will also let us
   // do mouse-event checks for only layer 30
	  %this.gridLayer.setLayer( 30 );
	  
	  for(%x = 0; %x < 8; %x++)
	  {
      for(%y = 0; %y < 8; %y++)
      {
         %this.setGem(%x, %y);
      }
	  }
}

function gridObj::setGem(%this, %x, %y)
{
   %num = %this.gems.getCount();
   
   echo("setting gem" @ %num);
   
   %gem = new t2dStaticSprite("gem" @ %num) {sceneGraph = t2dScene; };
   %gem.setLayer($layers::gemLayer);
   %gem.setImageMap(GreenChip);  
   
   %this.gems.add(%gem); 
   
   %pos = %this.getTilePosition(%x, %y);
   
   echo("pos: " @ %pos);
   
   %gem.setPosition(%pos);
   
   %this.images[%x, %y] = %gem;
   
   %this.board[%x, %y] = $greenChip;
}

function gridObj::getTilePosition(%this, %x, %y)
{
   // grab the board layer's position
   %tileMapPos = %this.gridLayer.getPosition();
   
   // divide the position up into x and y variables
   %tileMapPosX = getWord(%tileMapPos, 0);
   %tileMapPosY = getWord(%tileMapPos, 1);
   
   // grab the board layer's size
   %tileMapSize = %this.gridLayer.getSize();
   
   // divide the size up into x and y variables
   %tileMapSizeX = getWord(%tileMapSize, 0);
   %tilemapSizeY = getWord(%tileMapSize, 1);
   
   // calculate the start position
   %tileMapStartX = %tileMapPosX - (%tileMapSizeX / 2);
   %tileMapStartY = %tileMapPosY - (%tileMapSizeY / 2);
   
   // calculate the position and pass it back
   %pos = (%tileMapStartX + (%x * 64)) + 32 SPC (%tileMapStartY + (%y * 64)) + 32;

   return %pos;   
}