Apple Logic Pro /LogicExpress Discussion

I've had a Phonix Helix12 USB mixer for about a year, and I just got around to hooking it up.  Much to my dismay, neither my Imac G5 nor Imac Intel (2.0Gz) will recognize the mixer when hooked up with a USB cable.  I tested the cable.  According to the manual, the mixer should be plug and play with OS-X 10.4 and 10.5., yielding stereo in and out via the generic USB drivers.  

FYI both computers have no problems recognizing my generic USB headset microphone.   

The Phonic website is no help.  I am therefore asking m fine friends here for help.