it seems the problem occurs after the Soundbridge is switched off a longer period of time (e.g. over night). I can be pretty sure to have that issue when I come back home from work and switch it on.
It will never find the server. It will reboot in 90% after pressing ok to the message where it complains that there is no server. In the other 10% of cases, it will offer me the choice of servers and in this case, all three (Twonky, mt-daapd, and mt-daapd/rsp1.0) are available.
If you or Roku need more logs, I am hapy to provide them, as the combination between Roku and mt-daapd/rsp is marvelous.
An offside question: I was able to stream flac files on iTunes. Will that also work with Roku? And how is wma handled? Do I have to install something like flac on the server in order to allow streaming?