This does not sound like a Linux problem. It could be, if there is some other process running to interrupt things every so often, but both Twonky and Firefly are very stable under Linux - my current up-time is 125 days since my last reboot, and that was for hardware related reasons. What platform (hardware, Linux distro) are you using?
I suspect it is much more likely that your SoundBridge has a failing power supply (a very common problem if the unit is some years old), or that the connection to the server (wifi? wired?) is failing for some reason.
Which SoundBridge model do you have? This will help us point you in the right direction.
Roku M1000, M1001, M2000, R1000, Roberts WM-201, Stream 83i