This is the post that @Amitd was referring to... might help?
"Define a Javascript function that should be invoked if Flash loaded.
Invoke this method from the top of your Flash file.
Use a timer to detect if the callback is never invoked.
Prefer invoking Javascript functions from Flash rather than invoking Flash functions from Javascript. Either way you cannot invoke a function that has not been loaded yet. It is far easier to guarantee that the browser has finished loading your Javascript function before invoking it from Flash, than guaranteeing that Flash finished loading your Flash function before invoking it from Javascript.
Here is an example:
I am using swfobject to embed Flash.
I use FlashVars to tell Flash which Javascript function to invoke. This is useful if there are multiple Flash objects on the page.
Flash
var params:Object = LoaderInfo(this.root.loaderInfo).parameters;
if (ExternalInterface.available)
{
var onLoaded:String = params["onLoaded"];
if (onLoaded != null)
ExternalInterface.call(onLoaded, true);
}
Javascript
var flashLoaded = false;
var flashTimer;
function onFlashLoaded()
{
flashLoaded = true;
clearTimeout(flashTimer);
}
function onFlashTimeout()
{
if (!isFlashLoaded)
{
// Remove the Flash object in case it is partially loaded
$("#videoFeed").empty();
$("#videoFeed").append('<div id="flashObject"></div>');
alert("Failed to load video player");
}
clearTimeout(flashTimer);
}
function connectToVideo()
{
var flashvars = {};
flashvars.onLoaded = "onFlashLoaded";
var params = {};
params.menu = false;
var attributes = {};
isFlashLoaded = false;
flashTimer = setTimeout("onFlashTimeout()", 5000);
swfobject.embedSWF("flash/VideoFeed.swf", "flashObject", "800", "600", "11", "expressInstall.swf", flashvars, params, attributes);
}