X-CTU error "Incompatible function set selected for current module"

Hi, I'm trying to program two Digi XBee modules using X-CTU for use on an Arduino Uno - controlled robot. I am using a Sparkfun XBee Explorer to connect them to a laptop. When I try to write the settings to the XBee, however, it gives me an error "Incompatible function set selected for current module." I tried it with both XBee modules. For one the functions set was "ZIGBEE COORDINATOR API", and for the other it was "ZIGBEE ROUTER API". I updated the firmware, but it still doesn't work. Help is much needed. Thanks!

I'm trying to program two Digi XBee modules

You don't program them using X-CTU. You configure them. Which modules are you trying to configure?

For one the functions set was "ZIGBEE COORDINATOR API", and for the other it was "ZIGBEE ROUTER API".

These are function sets for series 2 modules. Do you have series 2 modules?

Actually, I might have Series 1 modules. I want to make one end the coordinator, to attach to my Arduino Uno via serial, and I want to use the I/0 pins on the router Xbee to control my robot. I know how to configure the I/O pins. What are the Series 1 equivalents of the function sets previously mentioned?

What are the Series 1 equivalents of the function sets previously mentioned?

Series 1 modules are point to point modules. There is no equivalent of a coordinator. Every device can talk to one other device, so each is a both a coordinator and an end device.

Thanks!