well no need to setup an pc with firefly if your soundbridge works like charm testing it in the room next to your wifi router.
now i would say, and i remember somehow, that wpa encryption changes the keys every 60 minutes but save the before used key for further 10 minutes. if your soundbridge doesn’t renew the key it disconnects after 70 minutes.
but i’m not really sure. fact is your belkin is misconfigured somehow. don’t have to be your error, could be a mistake by belkin.
but i have no idea how to fix this 🙁