Are USB drivers required to use Yamaha Keyboards with Mainstage?

Hey Gang,

We've got a M-Audio Keystation and as soon as we plug this keyboard in via USB to the Macbook Pro, it works flawlessly - we're using it in Mainstage or Logic.

However, when we hookup our Yamaha Motif the same way (same cable, via USB) we're not getting anything. I've gone into the MIDI Utilities on the Yamaha, and it's definitely set to use USB instead of MIDI. I can't figure out why it won't work.

Do we have to download and install Yamaha USB drivers on the host computer (MacBook Pro) for this to work? I found what appears to be a downloads/utilities for downloads at:

http://www.yamahaproaudio.com/downloads/firm_soft/index.html

We've got a service Sunday and REALLY need to use the Yamaha Motif instead of the Keystation, because we want to use sounds from both. Any help would be greatly appreciated.