I have had the same problem with my Futaba 6exh but that was because I had it on heli programming. As far as I know your doesn't have any heli functions but perhaps some form of mixxing got accidentally set.
Before sending it in for service start from scratch and reprogram that model.
If you do have to send it in you can send it to the Futaba service center. I have had good service from them in the past.
http://www.futaba-rc.com/service.html