I think it’s the soundbridge timing out when it wakes up and queries what devices are on the network.
I’ve seen this since the early 2 series of firmware on the soundbridge. I think it might be because the nslu2 takes a while to wake up — it has to spin up the drives and stuff, and maybe that makes the query timeout, and the soundbridge not see it.
Dunno. I can ask the soundbridge folks about it, though.