I've got an installation of IIS 5.0 on Windows 2000 Server, running an ASP.NET 2.0 web site which includes a web service.  Additionally, I have a virtual directory within the site pointing to a share on another computer - this is used to store media files that are exposed through the site.  Everything typically works as expected, and the site is used to host e-learning software (a lot of Flash and media) browsed via IE 6.0/7.0.

A recently uploaded Flash piece (generated through a software package called Articulate) has been having problems loading when clients access it...it hangs up for long periods of time (sometimes completely).  The Flash file actually performs its own additional GET calls to the server to load more files.  In doing an HTTP trace, it looks as if those assets (.xml and .swf files primarily) are taking a long time to load, after which my HTTP sniffer says that they've simply timed out (300 seconds).  In some cases there are 10-15 redundant calls for the same file within a given second.  Also, the Flash piece is loading these numerous assets at the same time as some Javascript in the page (in an .htc behavior) is making client-side calls to the site's web service.  The IIS logs indicate that there are indeed GET calls made for those assets (some redundantly), but IIS returns the HTTP status code 304 in each case, indicating that the content hasn't changed since last requested.  If I browse the troublesome assets independently in the browser, they're loaded properly and a 200 status code is returned.  Also, subsequent attempts to load the files after they're cached seem to work OK, as one might expect.  Interestingly, the HTTP trace logs seem to change each time the page with the Flash piece is loaded...different files often time out.  Sometimes it shows that the web service's .asmx file is also timing out, but in the IIS logs I can only find HTTP 200 status responses for the .asmx.

So, any votes as to whether this is an IIS issue, an ASP.NET issue, or a client-side IE issue?  Is it related to the web service calls happening simultaneously with the Flash player's attempts to GET files?  Any ideas?