I was trying to upload the Flash banner that I just finished up and kept getting the message “File type does not match security guidelines. Try another.”. I know there could be security concerns about uploading malicious files, but this is a one man show here. So I dug around and found this post about the problem. I looked in wordpress/wp-admin/admin-functions.php on line 1668 and added the MIME types that I needed. Works great!