I'm using mac os 10.6.8 - is the .inf file just for pc? I have a pc lying around here as well, so I will install the Rev3 driver on that and see what happens.
I have the exact same issue with my Arduino UNO R3. I have a regular Arduino UNO, which registers the USB port when plugged in - but when using the R3 - it fails to show the USB. Any idea why the R3 wont show up the USB and y old Arduino UNO will?