Starting with Flash Player 9 Update 3 (18.104.22.168) Adobe have implemented a strict policy on the format and meta type for the 'crossdomain.xml' policy file. This file must be collected by Flash Player before any text files can be read from a remote server, and is critical to the collection of TrackInfo, OGG and/or AAC audio by Muses Radio Player. Details of the changes can be found here.
The crucial chage for Icecast users is that the server content type for the file MUST be 'text/*', '*/xml', '*/aac' or '*/ogg'. The current builds of Icecast (2.3.1) have two ways to decide on the content-type for a file - firstly they try to locate the extension in the system mime.types file, then if they fail to locate it they default to using the content-type 'application/octet-stream'.
For Linux users: If your Icecast server is configured not to use 'chroot' setting, then it should be able to read the main Unix/Linux mime types file located at /etc/mime.types and all you need to do is make sure this file contains an entry for the XML file extension.
For Windows users: If your Icecast server has no mime.types, then all you need to do is to copy this file inside your icecast folder (by default should be "C:\Program Files\Icecast2 Win32").
If your Icecast server is configured to use 'chroot' setting, then it will look for the Unix/Linux mime types file but assume it is located at [Icecast install dir]/etc/mime.types and you must either create a link from there to the genuine file, or place a copy there. If you do not, then Icecast will believe the mime.types file is missing and use the default octet-stream content type, which will be rejected by Flash Player.
Users of Shoutcast or a proxy-based Muses Radio Player setup where the track data is served from a conventional webserver will normally have no issues, as their webserver will correctly identify the type for an XML file. If however the nowplaying data refuses to load, you should check that the content-type is valid by pointing your web browser directly at the nowplaying data URL, and using your browser's menu tools to check the header responses.
Note: This report is based on infomation published by DraftLight/MiniCaster at http://www.draftlight.net/dnex/mp3player/minicaster/pro/critical.php