ActiveX flash player and SWF files on a network

We've recently made a number of security-related changes to how UNC paths are handled in Flash Player, and in addition, have restricted some network requests from being made for locally-executed SWFs running with local-with-filesystem permissions.  These changes were necessary, as we found ourselves on the wrong side of a confluence of both old and emerging standards and conventions, and a very forgiving approaches to incorrectly constructed URLs in most major browsers.

Where we could, we added good debugging messages, so installing a an ActionScript debugger version of Flash and running the application might provide you with some useful clues; however, as complexity increases, I'm not convinced that using Flash Player to execute SWFs locally in the browser is going to be smooth sailing, and I anticipate that we'll see additional churn as we evaluate and align with the expectations of the modern web in this regard.

The good news is that we have Adobe AIR, which is designed to make it really easy to port your Flash Content, and it's specifically designed to build desktop applications, free from the complexity of browser plug-ins.  As a least-cost, long-term strategy, I'd strongly encourage you to evaluate porting your SWF over to AIR.  It may be as easy as just changing the publishing target in a current version of Flash Professional and distributing your application as an AIR payload instead.

Alternatively, you could stand up a local webserver and host both the content and the SWF.  The really hairy edge-cases stem from the fact that we're trying to support HTTP and UNC paths simultaneously.  If you're using HTTP, things are much, much more straightforward.

If you can narrow it down to the failing ActionScript call, I might be able to give you a more specific suggestion for a workaround.