Hi, my post #7, asked how you were powering the servo, and a circuit diagram please.
If you are using the 5V pin on the arduino, it possibly could cause your problem.
HOW ARE YOU SUPPLYING POWER TO THE SERVO, and a circuit diagram PLEASE.
Tom..... 
Hi, my post #7, asked how you were powering the servo, and a circuit diagram please.
If you are using the 5V pin on the arduino, it possibly could cause your problem.
HOW ARE YOU SUPPLYING POWER TO THE SERVO, and a circuit diagram PLEASE.
Tom.....