You've been using PMS since 2005? I'd like to see how that's possible, unless shagrath
had a private beta long before any public release...
Anywho, for music on the XBox 360, you need to enable the cache (Navigation/Share Settings -> "Enable the cache" checkbox) and then complete a full scan using the "magnifying glass" button.
This was discussed early on in the forum, but hasn't been brought up recently (looks like latest is viewtopic.php?f=6&t=7799&p=36327&hilit=xbox+mp3+music#p36327