Today I have uploaded the legacy Mac OS9.x compatible M-Audio Device Drivers to the Apple Mac Repository. M-audio Firewire 1814 Driver Mac Os X Sierra Pro.FireWire Solo Firewire 1814 Ozonic ProjectMix I/O ProFire Lightbridge NRV10: Operating Systems: Mac OS 10.6.8 (32-Bit) Mac OS 10.6.8 (64-Bit) Mac OS 10.7 Mac OS 10.7.1 Mac OS 10.7.2 Mac OS 10.7.3: Version: 1.10.3 (Mac) Release Date:: Release Notes.Fixed a problem that caused the M-Audio FireWire application settings to not be saved. Also it is worth noting that the upgrade from 10.5.3 to 10.5.4 broke some firewire drivers (I had that happen just a few weeks ago on a clients Mac Pro.
I agree on that having the latest drivers (currently named FireWire OSX1.8.4-3.dmg if you use OS X 10.5.3/10.5.4) is a must.