by Justin Hunt.
I think the original problem posted here, is probably not related to yours James.
In answer to your question though, Moodle uses a "filter" to parse the text being sent out and replace parts of it if necessary. So in most cases the multimedia plugins filter will see something like:
<a href="/i/like/listen/to/music.mp3">music.mp3</a>
And replace it with html audio tags or tags for a flash player. So you should check which filters you have enabled, and what the order of them is.
Also not everything gets put through a filter. So some places in Moodle, just won't get the player no matter what. The "attach a file" submission type of an assignment when displayed, is one of these ..I think.