Loading XML files in Flash over an SSL Connection in Internet Explorer fails if the Pragma:no-cache or Cache-control:no-cache HTTP headers are set on the XML file.
Wow! I’ve been chewing on this one for a while… We have a Flash site running on https with dynamically generated XML content. The server always returned the Pragma:no-cache header so that the dynamic data isn’t cached in the browser.
The bug is especially hard to find because the request goes out to the server successfully, but the XML object in flash remains undefined for no apparent reason. Only after removing the header output on the server it started to work.
This MS bug report seems to be related.
This post has been replaced by a more recent one, including an application to test the caching behavior of Flash in different browsers.
Some more posts on the topic: