It's a long shot, you could also try a few things. First, make sure all your motor wires are well away from the arduino/control wires, second, try putting a large (3.3kOhm or something) resistor between the servo pin on the arduino and ground, lastly if you can try a 0.1uF-1uF capacitor in it's place as well... Maybe one of those will help.
Oh and go back to the servo.h code

(now that I think about it, the capacitor is much more important than the resistor)