Xbee + Servo + Dual Shock 2 = HELP !

SoftwareSerial xbeeSerial(xbeeDO,xbeeDI);

Servo servo;

Probably unrelated to your current issue but SoftwareSerial and the Servo library tend to not work well with each other. Unless something has changed recently. Solution to Servo Jitters due to conflict between Servo.h and SoftwareSerial.h - Programming Questions - Arduino Forum