First, I know very little about Windows Server 2003 SE. So, this could be a ridiculously easy problem to solve, but I haven't found any information about it in a few searches using Google.
Anyhow, I've recently delivered a set of demonstration Flash applications to a customer to put onto their server. One application loads a file named app.cfg. On the customer's server this file fails to load. Flash errors report it as not found. If I attempt to access the file directly by entering the full path in the browser's address bar, the browser also reports the file as not found (conveying the message from the server). As a test, I asked the customer to create other files on their server named *.cfg. None of those files are accessible. I've concluded that the web server will not currently deliver *.cfg files. How can they tweak their web server settings to allow *.cfg files.
Modifying the Flash application and renaming the cfg file isn't a solution.