This is not a bug in Playback
The most common cause of this problem is having more than one router on your network. UPnP discovery relies on UDP multicast, which simply doesn’t work through multiple routers. Unfortunately, there’s nothing we can do about this; it’s inherent to the design of the protocol.
Also, connecting the Xbox or Playstation directly to your computer via an Ethernet cable is not a supported configuration. The Microsoft-designed UPnP specification provides UDP multicast as the only means of service discovery. Multicast traffic typically requires the presence of a router.
If you have another UPnP media server installed on your system, Playback cannot respond to your device’s search requests. In this case, there are two solutions:
1. Uninstall the other software and restart Playback Server.
2. Restart Playback Server whenever you wish to access your media.
When restarted, Playback Server will broadcast its presence to all UPnP devices on your network. This should cause Playback to appear on both the Playstation 3 and Xbox 360.
If the above doesn't work:
Unfortunately, it's extremely difficulty to troubleshoot UPnP discovery issues remotely. You'll need to run a packet capture application to get the information we need to track this down.
There's a free one with a decent GUI here:http://sourceforge.net/projects/packetpeeper/
Make sure Playback is enabled and then launch Packet Peeper and select "New Capture..." from the File menu. Enable "Promiscuous capture mode". Switch to the Advanced tab and enter:
udp port 1900
Click "Start" to begin capturing traffic.
Now select "Search for Media Servers" on the PS3. You should see some traffic appear in Packet Peeper. If you don't, your network is not routing UPnP discovery traffic to your computer.