I applied the DSM 4.0 update to my DS210J today. Even though Media Server is running no devices on the network 'see' the server. Prior to this I had no problems streaming audio, video or pictures to my PS3 or Xbox.
I have stopped and restarted the Media Server and rebooted the Disk Station, still no love.
Has anyone else encountered this problem? If so, were you able to resolve it? On the flip side, if you upgraded to 4.0 and your PS3 or XBox still sees the media server let us know
UPDATE: Problem solved - the problem was the firewall on the DiskStation. I needed to add rules allowing the media server. I then rebooted the server and my router and everything works.