IE can't load embedded swfs on the Internet, but can access them locally

Question

We have two Windows Embedded Standard machines that have suddenly started failing to load embedded swfs over the Internet via IE, but then they're able to load them just fine when the HTML wrappers are on the computers themselves. It's that "Movie not loaded..." error. But they had been working for a very long time, and they have not received any sort of updates to our knowledge; but if we try to pull out Firefox, suddenly we can load the Flash movies again.

We've been trying to do a mixture between both solving the problem and figuring out what originally caused this. We've tried using Windows Updates, upgrading IE, reinstalling Flash Player, upgrading Flash Player, deleting data/cache out of IE and FP, loosening every security setting we could identify in IE, skimming over logs in Event Viewer, etc. And nothing has changed on the server that the machines load the pages from or with the networking.

But it's not just that one server that they're having trouble with; we've tried several different web pages across the Internet. The computers will load a swf embedded into an HTML/ASP page via IE if and only if it is on the computer itself (or at least in the internal network or something). But embedding jpgs works perfectly fine with those machines, and typing in the address of the swf itself into the URL bar works perfectly fine.

Where else can we look? Thank you.

Answer 1

Well, the theory at the time was that nothing with the networking had changed, and depending on how you look at it, that may or may not be true. It wasn't a firewall issue per se, but it did turn out to be an issue with a web filter the client was using.