encyclo - 1:14 am on Sep 9, 2006 (gmt 0)
If the validator didn't give a warning about the mime type, then that's a good sign - it usually means that the server is already handling things correctly. Can you load/view the feed in a browser? If you have Firefox, when you visit does it show an XML view or offer a download prompt? If you get an XML view, press Ctrl + I and check what "Type" is listed, as well as the encoding.