max, arduino, xbee

sorry, a bit new here. can somebody explain how i can send data from software (a max patch in this case) through an arduino sketch and then out an xbee? it seems like this should be simple, but my xbee will only transmit when my shield is jumpered to "xbee", which seemingly cuts off usb port input.

if i dechip my arduino and use the "usb" jumper settings things work fine -- but then i can't use the nice xbee-arduino library.

i have a feeling i am missing something obvious...