Thank you, Miller, for looking into this
Using pd~ 0.4 in Max 7.34 with PD 0.50-2 on Mac OS 10.9. i find this error:
[pd~ -ninsig 2 -noutsig 2 -fifo 10] leads to right channel (2) not receive anything from PD, while the max patch (same with the help file associated with pd~) the right channel shows complete overload on the meter.
Just for a difference i tried 3 channels instead [pd~ -ninsig 3 -noutsig 3 -fifo 10] moves the problem (including displayed overload) to channel 3, now channel two works with PD.
Might help debugging.