I'm a little confused by this entire description, all these processors and RF devices.
To me, it sounds like you got ahead of yourself, hooked up everything and tried to
get it all to work at the same time. The only way to do a project of this complexity
is one step at a time.
- first, forget about the RF part and the extra controller boards.
- go to the basics, use 1 controller with "wired link" between Arudino and PC,
and get your sketches to work, including your servo code. - add whatever else you want, controllers or sensors, "except" the RF link.
- once that's working, then go to using the RF link.
Also, if you're trying to download sketches to the Arduino using this lashup, forget it.
You can't do it. Also, I personally have not had good luck with the SoftSerial libraries,
so I connect the Arduino hardware UART [RX,TX pins] alternately between my PC via
USB, and my RF devices [XBee in this case].