i'm not very familiar with the Saffire, other than seeing some descriptions (a year or so ago), but as long as it and its drivers are compatible with Macs, as well as the version of OS you're using, it should work with GB
IOW, if it works on a Mac as an audio interface, it will work with GB.
actually, that's the first thing i'd check, make sure you have the latest drivers. there's a link here:
http://www.bulletsandbones.com/GB/Drivers.html