Over the air firmware upgrade

Here is my set up. I will have a Xbee 900 on a Dev board connected to a 9Xtend on a Dev board. The two dev boards are connected via RS-232 with a null modem cable. These two units are mounted on top of a 200 foot tower. I am using the 9Xtend as a repeater and the Xbee 900 to change the parameters on the 9Xtend. I can change the parameters without a probelm but I am needing to change the firmware on the 9Xtend. I have CTS and RTS enable on all radios. I am getting an error when X-CTU tries to read the AT parameters at the beginning of the firmware update. What might I be doing wrong or what might I need to do so I do not have to climb the tower to update the Xtend radio.