avrdude error

I am getting this error running a sketch to test an ultrasonic sensor:

avrdude: verification error, first mismatch at byte 0x0200 0xb0 != 0xff avrdude: verification error; content mismatch

Here is the code:

#define trigPin 13
#define echoPin 12

void setup() {
  Serial.begin (9600);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);

void loop() {
  long duration, distance;
  digitalWrite(trigPin, LOW);

  digitalWrite(trigPin, HIGH);
  digitalWrite(trigPin, LOW);
  duration = pulseIn(echoPin, HIGH);
  distance = (duration/2) / 29.1;
  if (distance >= 200 || distance <= 0){
    Serial.println("Out of range");
  else {
    Serial.println(" cm");

For which Arduino? This particular error is almost always caused by having the wrong board selected.

It is an Uno R3. I just double checked that it was properly selected in the IDE.

I just ran the Blink sketch and I get the same thing.