It is very weird... same problem here, I found a solution though not a very good one, the app opens when the device is unplugged, so for the mo, unplug the firewave, open the app, plug it again... works for me.
if it doesn't do this: 1. Close the FireWave software and unplug FireWave from your computer.
2. Move the following files to the trash:
Applications > FireWave
Home > Library > Preferences > com.griffintechnology.FireWave.plist
3. Empty the trash.
4. Repair your disk permissions. To do this, open Disk Utility. It can be found in the Utility folder in your Applications. In Disk Utility select your hard drive and click the “Repair Disk Permissions” button. After this process has completed, restart your computer.
5. Restart your computer. (before you restart make sure the Firewave is unplugged.) (after you download open the application first then plug in the Firewave)
6. Download and install the latest FireWave software:
http://www.griffintechnology.com/support/products/firewave/
(after you download open the application first then plug in the Firewave)
it still only works when the device is unplugged, but at least, it allows 5.1 sound... hope this helps... if someone has a better solution I'll appreciate it.
Bye!