It has been noted that there are a few important changes to Joomla! that come with the 1.5.15 update that should be noted. They made some changes to the .htaccess file (htaccess.txt in the upgrade package) that deny access to all xml files on your directory. This is great as it disallows access to your xml files so that hackers can’t use them to see your extension version info.
The only problem with this is if you want any of your xml files to be publicly accessible (xml feeds, google xml feed for webmaster tools, etc.), you will need to put exceptions for those individual files in your .htaccess file . . . which honestly is a pain if you have several xml files you want to be viewable.
OR, if you are one of our Joomla! hosting customers, your xml files are already protected by our server configuration. So, thank you Joomla! for realizing and offering a fix for this for those whose sites are not on a Joomla! optimized host. Not having to worry about this is yet another benefit of hosting with Simple Source Solutions.