sketch for uno SMD r2 vs uno r3

I successfully used the following sketch(see below) for my UNO Rev3 board but can't use it with my recently purchased UNO SMD Rev2 board. Instead, get error message: Binary sketch size: 1,128 bytes (of a 32,256 byte maximum) avrdude: stk500_recv(): programmer is not responding Not sure what the difference is between the Rev2 and Rev3. Fairly simple sketch. Any help would be greatly appreciated. Thanks, Mark

// Pin 13 has an LED connected on most Arduino boards.
// give it a name:
int led = 13;

// the setup routine runs once when you press reset:
void setup() {                
  // initialize the digital pin as an output.
  pinMode(led, OUTPUT);     
}

// the loop routine runs over and over again forever:
void loop() {
  digitalWrite(led, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(300);               // wait for .3 second
  digitalWrite(led, LOW);    // turn the LED off by making the voltage LOW
  delay(200);               // wait for .2 second
  digitalWrite(led, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(300);               // wait for .3 second
  digitalWrite(led, LOW);    // turn the LED off by making the voltage LOW
  delay(3000);               // wait for 3 seconds

}

Check your COM port number for the Rev2.

Larry, thanks for your response. After using a Mac for over 20 years, I haven't a clue how to confirm a COM port connection?? Easily found on a Windows machine but I'm currently using Mac OS 10.8. I'll do some research and get back to you. Thanks again, Mark

Thanks Larry. You nailed it! Easy fix involved selecting the correct port. In my case... Tools>Serial Port>/dev/tty.usbmodem1421

Thanks again, Mark