Users with a non-English Mac OS may have later versions of the FireWire extensions that do not have a particular feature found in the v.2.5 or later North American version - callback at interrupt priority - this is required in order for Digi 002 FireWire drivers to load. Additionally, some versions of the Mac OS may not even allow the customer to use the older 2.5 North American Versions.The customer must download the FireWire developer kit from Apple's web site. The Apple FireWire developers kit includes version 2.8.1 of the extensions. This should work with any OS. The link is ftp.apple.com the package is extracted go into the FireWire 2.8.1 SDK>Extensions>FW Extensions>FireWire 2.8.1 (TM)> and copy these 2 extensions over what is currently loaded in the system (be forewarned that the names may be different with different languages but the icons will always be the same).