If you like the flash player to expire the content of the SWF file add the following line between your <HEAD></HEAD> tags
<META HTTP-EQUIV="Expires" CONTENT="Mon, 04 Dec 1999 21:29:02 GMT">
for more information check out:
http://kb2.adobe.com/cps/147/tn_14743.html
To prevent flash caching xml data, you can use the cache manager extension. It basically adds a timestamp to the querystring so it looks like a unique request.
You can download this from here:
http://www.communitymx.com/content/article.cfm?cid=827ea
Once you install the extension the usage is quite simple:
xml.load(CacheManager.uncacheURL(XmlFileLocation));
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