I had posted earlier concerning a strange issue with Flash Player 10 where the SWF would refuse to load if being served over a Java servlet. We’ve been able to resolve the issue by explicitly transferring any SWF content with a “Content-Disposition” header of “inline” as suggested by Adobe. The relevant portion of this document is replicated below:
Starting with version 10,0,2, if Flash Player sees a “Content-Disposition: attachment” header while downloading a SWF file, it will ignore the SWF file rather than play it. Note that this restriction applies only to SWF files and not to other types of content, such as images, sounds, text, or XML files, policy files, etc.
If you control the HTTP server on which the SWF file resides, determine whether you trust the SWF file to execute in the server’s domain. If so, remove the “Content-Disposition: attachment” header by changing your HTTP server’s configuration.
While our resolution did differ slightly from the one posted above. It effectively does the same thing.