I have a white Macbook 1.83Ghz, 512MB (soon to be upgraded to 2GB )and a fresh out of the box trigger finger.
Plugged it in the USB and the LED's came on. Tried to set it up in preferences, selected Trigger Finger and nothing else happens, i can't select the input and output.
I discovered that my Trigger Finger was funky (periodically it would stop communicating with my Macbook) using the USB port closest to the front of the laptop. When I switched to the rear port all issues (seem) resolved.
I posted this in another thread, according to M-audio, macs are known to have underpowered USB ports. The guy also said that Apple is aware of the problem and they're working on it.