Async loading of test swf is never caught by listener

Question

Hi all,
I'm really struggling getting a testing structure in place. I need to test a sub-swf which gets loaded into a range of main applications and its methods are then invoked. Therefore, I want to setup a test initially to load in that sub-swf (before calling its functions).
However, despite Firebug revealing that the swf in question was called ok (200 return) the timeout function always eventually is invoked.
Please can someone tell me what I'm doing wrong as I've been struggling with this for over a week.
Code roughly copy-and-pasted (no errors when I run the original)...
public class loadSWFTester
import flash.display.Loader;
import flash.display.LoaderInfo;
import flash.events.*;
import org.flexunit.asserts.*;
import org.flexunit.async.Async;
private var _loader:Loader;
private var _request:URLRequest;
[Before(async)]
public function setUp():void
_loader = new Loader();
_request = new URLRequest("http://example.com/my.swf");
[Test(async, description="Swf load example")]
public function loadSwf():void
_loader.addEventListener(Event.COMPLETE, Async.asyncHandler(this, verifySwfLoad, 10000, null, handleTimeout));
_loader.load(_request);
private function verifySwfLoad(event:Event, passThroughData:Object):void
trace("[verifySwfLoad");
private function handleTimeout(event:Event):void
fail(" testLoad did not execute: "+event);

Answer 1

If I specify a non-existant URL then I get this error:
Error #2044: Unhandled IOErrorEvent:. text=Error #2035: URL Not Found.
...so the previous URLs I've been specifying must've been verified by the Flash player before failing in some respect somewhere else.
No event listeners seem to pick up on anything. I've tried adding a few extra (not in the example link I supplied previously yet) but the timeout function is the one which is always hit.
_loader.addEventListener(Event.INIT, Async.asyncHandler(this, initHandler, 10000, null, handleTimeout));
_loader.addEventListener(IOErrorEvent.IO_ERROR, Async.asyncHandler(this, onIoError, 10000, null, handleTimeout));
I've tried moving these listeners up in the [Before] block too with similar results.