you are likely to run into a power supply issue here. The XBee must be powered with 5V on pin 5. The 10pin Atomboard connection does not provide power to the XBee.
If you want to use an XBee on the Atomboard, I recommend to either use a direct USB connection (with an USB XBee of course) or use the AscTec USB<->serial adapter in between. The adapter provides the power to the XBee.