No movement from servo motor

Hi,
I was doing project 5 from the arduino starter kit and once everything was set up and the code was written and uploaded, the servo motor would twitch, but the arm would not move.
Here is my code:

#include<Servo.h>
Servo myServo;
int const potPin=A0;
int potVal;
int angle;

void setup() {
  // put your setup code here, to run once:
myServo.attach(9);
Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly:
potVal=analogRead(potPin);
Serial.print("potVal: ");
Serial.print(potVal);
angle=map(potVal,0,1023,0,179);
Serial.print(",angle: ");
Serial.println(angle);
myServo.write(angle);
delay(30);
}

How do I get the motor to move to the appropriate angle?

Thanks!

Has the servo worked with other code like below?

//zoomkat 7-30-10 serial servo test
//type servo position 0 to 180 in serial monitor
// Powering a servo from the arduino usually *DOES NOT WORK*.

String readString;
#include <Servo.h> 
Servo myservo;  // create servo object to control a servo 

void setup() {
  Serial.begin(9600);
  myservo.attach(9);
  Serial.println("servo-test"); // so I can keep track of what is loaded
}

void loop() {

  while (Serial.available()) {
    char c = Serial.read();  //gets one byte from serial buffer
    readString += c; //makes the String readString
    delay(2);  //slow looping to allow buffer to fill with next character
  }

  if (readString.length() >0) {
    Serial.println(readString);  //so you can see the captured String 
    int n = readString.toInt();  //convert readString into a number
    Serial.println(n); //so you can see the integer
    myservo.write(n);
    readString="";
  } 
}

You have a good power supply for the servo?