Some threads, mainly at the roku forums suggest wifi problems with these kind of problems , but I’m guessing this must be something else, because the WMC over wifi is stable at all times.
The Soundbridge 2.7 firmware seems to have quite a few issues although, in normal Roku fashion, they haven’t acknowledged anything. Possibly because they haven’t found anything conclusive. However, they do seem to be downgrading people to 2.5 on request so that might be a good starting point. Also, if you want to try it the latest nightlies seem very stable on the slug. I’ve been running 1489 for some time without incident.