I have been having a similar problem with my LeafLabs Maple Rev.5 (An Arduino clone with an ARM processor) and my Mac (running the latest version of Lion). When I connect it, I am NOT prompted by System Preferences to create a new modem, causing the board not to be displayed in the list of ports. I've tried ls -l /dev/tty.usb* , but it does not return anything. This problem is rather puzzling to me.