Precis: External interface doesn't work if your applet is really invisible. External interface doesn't work in Internet Explorer unless you're loading the SWF during page load.
An XML declaration is not required in all XML documents. Such a declaration is required when the character encoding of the document is other than the default UTF-8 or UTF-16.
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.
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.