SoundBridge is OK and doesn't require a restart in this scenario. Firefly is very dead. I can't connect to it from another SoundBridge or iTunes. (DAAP or RSP.) But the process continues to run... iTunes, for example, hangs on "Loading..."
There seem to be two different things you are reporting. One sounds like a sb problem, one seems like a ff problem.
On the ff one, what version are you running? Can you check the version tab on the config and verify you are running the matched version plugins. Also, can you test with a group a files with the same codec?
I can't make it behave as you describe with 1156, using ogg, mp3 or wma. If you could narrow it down to a codec type that consistently does it, It would help.
Your windows machine, is it XP or 2000?
EDIT: I did just now get my sb to reboot by doing what you describe... running quickly up and down a playlist. It was a playlist composed entirely of wma files served natively to the sb.
I'm still trying to get ff to hang, though.