Reboot the Soundbridge. This is an (old) known bug the SBs have.
Apparently Roku doesnt think this one deserves priority. I think this is a shame, because one often checks EVERYTHING else in the chain, only to find the last piece to be faulty. 🙁
Well, another thing you can do is using the Avahi-Browser under Ubuntu. Then you can see the multicasts, etc.
Doesnt make much sense on the same host though, but on the WLAN, prolly. You get the idea.