Arduino mini requires uploading on every power up? My Arduino mini is experiencing some really strange problem.

I'm using the BlinkWithoutDelay example sketch for testing:

const int ledPin =  13;
int ledState = LOW;             // ledState used to set the LED
long previousMillis = 0;        // will store last time LED was updated
long interval = 1000;           // interval at which to blink (milliseconds)

void setup() {
    pinMode(ledPin, OUTPUT);      
}

void loop()
{
    unsigned long currentMillis = millis();

    if(currentMillis - previousMillis &gt; interval) {
    // save the last time you blinked the LED 
    previousMillis = currentMillis;   

    // if the LED is off turn it on and vice-versa:
    if (ledState == LOW)
        ledState = HIGH;
    else
        ledState = LOW;

   // set the LED with the ledState of the variable:
   digitalWrite(ledPin, ledState);
  }
}


The program basically turns pin 13 on and off every 1000ms.

When I uploaded this sketch into the mini (via Arduino Uno board, sans Atmega chip), the scope reading of pin 13 shows nice square waves (1s pulsewidth, 2s period), as expected.

I then unplug the USB cable powering the mini through the Uno board, wait for a few seconds for the scope traces to settle (I only have an old analog one at hand), and then plug it back in to turn on the board. However, the pin output is different - I now get a train of three pulses (60ms wide, 60ms between pulses) at sporadic intervals.

Uploading the sketch then yields the desired square waves again.

What is going on here? I'm fairly sure the mini has nonvolatile memory and it's intact (otherwise the bootloader through which I upload the sketch would not work).
There was a defective bootloader that shipped on some Arduino devices which caused the symptom you describe. See:

http://forum.arduino.cc/index.php?topic=51172.0

http://forum.arduino.cc/index.php?topic=74090.0

If that's the case, your options are to re-write the bootloader yourself (if you have the capability) or return to the manufacturer.