Thanks, Josh...Bpod does indeed seem to run when specifying the proper Arduino serial port! While it loads using the high latency Matlab/Java serial interface, I'm running into trouble when I try connecting with the PsychToolbox interface. Matlab hangs in BpodObject.m when trying to test the serial port, specifically when trying IOPort('Write'). I'm hoping that Bpod can work in low latency mode with an appropriate sound card on the Mac--but perhaps that's asking a bit much right now?
My wish is ultimately to use Bpod for low latency delivery of high frequency sounds--I realize that you've come up with a nice solution using the Asus Xonar DX sound card and moving to Windows is probably the simplest option. I agree with your earlier post regarding Bpod Audio that a low-cost, low-latency, high-definition sound server would be a great addition!