What I recommend is creating a /flex directory in your preferred location (mine is on the root of C:) where you have all your SDKs, and put a folder there called /playerglobals where you have all your versions of playerglobal that you will need.
Then delete the FlexSDK_x.x.x/frameworks/libs/player folder from every SDK and replace it with a Directory Junction (hard) link, which you can do with the following command (Windows):

mklink /J C:\flex\FlexSDK_x.x.x\frameworks\libs\player c:\flex\playerglobals

Now you have only one place to worry about your playerglobals.

Or to be specific, it will not work in the Metro Internet Explorer 10 browser.

According to this MSDN article, your flash content will not be displayed unless it has been whitelisted by Microsoft.
If you want users to be able to see your flash content you have two options:

1. Add the http header
   “X-UA-Compatible: requiresActiveX=true”
   or the meta tag
   “<meta http-equiv=”X-UA-Compatible” content=”requiresActiveX=true” />”
   to your site, which will prompt the user to open the page in Desktop IE.
   
2. Send an email to Microsoft and request your page to be whitelisted, which can take up to 6 weeks + 1 month to get into effect.
   “Microsoft will process the developer’s request in approximately six (6) weeks”
   “Sites accepted onto the CV list will be included in the next regular update of the CV list, which Microsoft updates to end users of Windows 8, typically one time per month.”

Windows 8 is coming out on October 26^th, is your webpage ready?

This allows you to have a switch-case for an object’s class:

function addShape(shape:Shape):void {
	switch (Object(shape).constructor) {
		case Circle:
			trace("It's a circle");
			break;
		case Square:
			trace("It's a square");
			break;
		default:
			trace("Unknown shape");
	}
}

Which flash files break and which don’t depend on one thing; if you are using JavaScript to prevent the default behavior of the mouse scroll wheel or not.

The reason for preventing default mouse scroll wheel behavior is for when you don’t want the page to scroll when you scroll over the flash content.
To prevent that, developers write JavaScript code (or use libraries like SwfWheel.js) that add an event listener for the “mousewheel” or “DOMMouseScroll” event, and in the handler call “evt.preventDefault()” and/or “evt.returnValue = false” to cancel the scroll.

Therein lies the problem, the old NPAPI Flash Player would receive the mouse scroll event even if we prevented the default behavior. Maybe even incorrectly so, since the event was cancelled.
The new PPAPI Flash Player will not receive the event if the default is prevented.

If one were to remove the preventDefault() function, the Flash file would start working correctly again, but the whole page would again start scrolling, which is out of the question.

You will have to not only prevent the default scroll behavior, but also call an external interface function in your flash file to let it know when the user scrolls the mouse wheel.
In my case I was using SwfWheel and only needed a small modification to the library file: in the SWFWheel.getState() function add this code before the “if (br.mac)” line:

// The new pepper plugin requires chrome to always be hacked.
if (br.chrome)
{
	return STATE_HACKED;
}

The solution seemed to be to remove all traces from try-catch blocks, which worked, but I wasn’t satisfied.

After binary searching trough the svn commits, I found what triggered the above error, an empty for-each loop.
Removing that loop made all traces work again normally inside try-catch blocks, which is what I prefer.

for each (var fruit:String in fruits) {
   // Empty loop, a BIG NO NO!
}

So to prevent your swf from corrupting, do not have empty for-each loops in your project! Remove them completely or fill them with some code.

If you have a throw statement before the super() in the constructor, Flex will complain with the following error code:
1201: A super statement cannot occur after a this, super, return, or throw statement.

There is a workaround though, just wrap the throw statement in an anonymous function:

(function():void {
	throw new Error("Yay for workarounds!");
})();

Facebook has a solution for you, on FB.init you can set your own callback function via the hideFlashCallback parameter. In this callback you can move the flash object out of view by, for example, setting the top to be -10000px whenever a Facebook dialog is opened and then putting it back when the dialog is closed.

I had functions registered with external interface to pause and resume the game that would get called via javascript in the hideFlashCallback callback.

This was working well enough but for some reason on Internet Explorer I couldn’t call the resume() function just after showing the flash object, instead I got an “Object Expected” error.

Internet Explorer does not support calling external interface methods for flash objects if they are not visible. Since it could be a race condition (DOM might not render the flash object before the function was called) I added a 100ms delay to the call to resume(), only for IE. This seemed to work fine.

But once we got close to production this error re-appeared, but only when Facebook’s purchase dialog had been shown. Weird! No amount of delay made the external interface calls work again. If I showed the purchase dialog once and closed it, it would be no longer possible to call any external interface functions for the flash object until a page refresh. This was not acceptable.

After a lot of debugging, I noticed that even though we have registered for the hideFlashCallback function, facebook STILL sets the visibility of the flash object to “hidden” after 200ms.

As can be seen in Facebook’s documentation: “The custom action must complete within 200ms or the Flash object will be hidden automatically regardless.”

Apparently the fact that we’re changing the visibility of the flash object along with whatever facebook does differently during the purchase dialog (overlay a white div over the whole page) breaks all external interface functionality.

This has a simple fix though, create a higher priority CSS rule that makes the flash object always visible:

It doesn’t need to be hidden since we are moving it out of view ourselves anyways.

After the workload decreases I should be able to start writing again, I have some PureMVC stuff I’m dying to write about.

Googling around yielded no results, so after figuring out the problem I’m posting the solution here for anyone else having this problem.

The solution is short: you have to call drawToBitmapData() BEFORE the Context3D.present() call.

In my case with Starling I had to add the functionality in the Starling.render() function, between the call to mStage.render() and the call to mContext.present().