Project 08, if led gets to 76 it gets all weirded out. Why? =)

Hardware The Arduino Starter Kit
1

Wanting to see things quickly in project 08 I made interval 200.

This is great, and means you don't have to wait an hour too see the thing working. But a curious thing happens, it all works as expected... but after a certain length of time the whole hourglass starts all over again!

So I got curious and added some debug code, namely printing out the value of led. And when led gets to 76 things go weird. Can anyone explain this to me?

sketch:

/*
  Arduino Starter Kit example
 Project 8  - Digital Hourglass
 
 This sketch is written to accompany Project 8 in the
 Arduino Starter Kit
 
 Parts required:
 10 kilohm resistor
 six 220 ohm resistors
 six LEDs
 tilt switch
 
 Created 13 September 2012
 by Scott Fitzgerald
 
 http://arduino.cc/starterKit
 
 This example code is part of the public domain 
 */

// named constant for the switch pin
const int switchPin = 8;

unsigned long previousTime = 0; // store the last time an LED was updated
int switchState = 0; // the current switch state
int prevSwitchState = 0; // the previous switch state
int led = 2; // a variable to refer to the LEDs

// 600000 = 10 minutes in milliseconds
long interval = 200; // interval at which to light the next LED 

void setup() {
  // set the LED pins as outputs
  for(int x = 2;x<8;x++){
    pinMode(x, OUTPUT);
  }
  // set the tilt switch pin as input 
  pinMode(switchPin, INPUT);

 Serial.begin(9600);
}



void loop(){ 
  // store the time since the Arduino started running in a variable 
  unsigned long currentTime = millis(); 

  // compare the current time to the previous time an LED turned on
  // if it is greater than your interval, run the if statement
  if(currentTime - previousTime > interval) {
    // save the current time as the last time you changed an LED 
    previousTime = currentTime; 
    // Turn the LED on
    digitalWrite(led, HIGH);
    // increment the led variable
    // in 10 minutes the next LED will light up   
    led++; 
    
    Serial.print("led: ");
    Serial.println(led);
    
    if(led >= 7) {
    Serial.print("led is more than 7!!!!!!!!!!!! ");  
    }
  }

  // read the switch value
  switchState = digitalRead(switchPin); 
  
  // if the switch has changed
  if(switchState != prevSwitchState){
    // turn all the LEDs low
    for(int x = 2;x<8;x++){    
      digitalWrite(x, LOW);
    }  
    
    // reset the LED variable to the first one
    led = 2;
    
    //reset the timer
    previousTime = currentTime;
  }
  // set the previous switch state to the current state
  prevSwitchState = switchState;
}

typical readout:

led is more than 7!!!!!!!!!!!! led: 70
led is more than 7!!!!!!!!!!!! led: 71
led is more than 7!!!!!!!!!!!! led: 72
led is more than 7!!!!!!!!!!!! led: 73
led is more than 7!!!!!!!!!!!! led: 74
led is more than 7!!!!!!!!!!!! led: 75
led is more than 7!!!!!!!!!!!! led: 76
led is more than 7!!!!!!!!!!!! led: 4429
led is more than 7!!!!!!!!!!!! led: 4430
led is more than 7!!!!!!!!!!!! led: 4431
led is more than 7!!!!!!!!!!!! led: 3
led: 4
led: 5
led: 6
led: 7
led is more than 7!!!!!!!!!!!! led: 8
led is more than 7!!!!!!!!!!!! led: 9
led is more than 7!!!!!!!!!!!! led: 10
led is more than 7!!!!!!!!!!!! led: 11
led is more than 7!!!!!!!!!!!! led: 12

etc

Seems it's maybe some sort of memory thing? Because when I make the fabulously informative write " Serial.print("led is more than 7!!!!!!!!!!!! ");" have a few more exclamation marks in it it starts to behave differently