Seeking through a streamed MP3 file with HTML5 <audio> tag
Make sure the server accepts Range requests, you can check to see if Accept-Ranges is in the header. In jPlayer this is a common issue in Webkit (particularly Chrome) browsers when it comes to progress and seeking functionality.
You might not be using jPlayer, but the Server Response information on the official website may be of some use.
http://www.jplayer.org/latest/developer-guide/#jPlayer-server-response
have a look here http://www.scottandrew.com/pub/html5audioplayer/, I used this and it plays while it is downloading the file. It waits a little bit for the buffer but then plays. Never tried seeking though but I would start by trying to set the "aud.currentTime" in his code if that can be done.
Good luck