Weird problem: some text not showing on some Macs

The text created in the code below shows 99% of the time on both PCs and Macs, but sometimes it wont show on Macs. There seems to be not reason for it. I havent been messing with the code. :expressionless:
This creates the links:
[AS]private function createText () : void {
for each (var i:XML in vidXML.item) {
vidThumb = new VideoThumb(i.@name, i.@file);
vidThumb.y = newHeight;
newHeight = vidThumb.y + vidThumb.height;
vidThumb.addEventListener (‘LINK_CLICKED’, clicked);
linkHolder.addChild(vidThumb);
}
}[/AS]
[AS]package {

import flash.display.Sprite;
import flash.events.MouseEvent;
import flash.events.Event;
import flash.net.URLRequest;
import flash.text.TextField;
import flash.text.TextFormat;
import flash.text.AntiAliasType;
import flash.text.TextFieldAutoSize;
import flash.geom.ColorTransform;
import caurina.transitions.Tweener;

public class VideoThumb extends Sprite {		
	
	private var vidFile:String;		
	private var vidName:String;			
	private var _vid:Sprite = new Sprite();			
	private var txtField:TextField = new TextField();
	private var format:TextFormat = new TextFormat ();
	private var linkClickEvent:MouseEvent = new MouseEvent ('LINK_CLICKED', false,false);
	
	public function VideoThumb (vidName:String, vidFile:String) {
		this.vidName = vidName;
		this.vidFile = vidFile;			
		this.addEventListener(MouseEvent.MOUSE_OVER, over);
		this.addEventListener(MouseEvent.MOUSE_OUT, out);			
		init();			
	}		
	
	private function init():void{			
		
		format.size = 14;
		format.font = new Helevetica ().fontName;
		format.color = 0x333333;
		format.align = 'left';						
		
		_vid.buttonMode = true;
		_vid.useHandCursor = true;
		_vid.mouseChildren = false
		_vid.addEventListener (MouseEvent.CLICK, down);
		
		txtField.embedFonts = true;
		txtField.defaultTextFormat = format;			
		txtField.antiAliasType = AntiAliasType.ADVANCED;
		txtField.autoSize = TextFieldAutoSize.LEFT;
		txtField.wordWrap = true;
		txtField.multiline = true;
		txtField.selectable = false;			
		txtField.text = vidName;

		txtField.width = 400;
		
		_vid.addChild(txtField);
		addChild(_vid);
	}

	private function down(evt:Event){
		dispatchEvent(linkClickEvent);			
	}
	
	private function over(evt:MouseEvent){
		Tweener.addTween (this, { time:0.5, alpha:0.5 } );
	}
	
	private function out(evt:MouseEvent){
		Tweener.addTween (this, { time:0.5, alpha:1 } );
	}
	
	public function get fileID () : String {
		return vidFile;
	}
}

}[/AS]
has anyone come across a similar problem? any ideas?