I hadn’t used PS3 Media Server on my headless box for a long time, but when I tried it this evening I noticed that it was no longer showing up in any of my UPnP clients.
The log files looked perfectly normal and after triple-checking the configuration I noticed that the problem seemed to be that PS3 Media Server seemed to be binding to the IPv6 interface of my NIC, and not the IPv4 one. I’m not quite sure of why this happened but thankfully you can force the interface to bind to by specifying the IP address in PMS.conf like so:
hostname = <your_ip_address>
After you make the change, just restart PS3 Media Server and hopefully it will show up again for you.
 Ubuntu 12.04 Server 64-bit, w Sun JDK 1.6.0 26.