xBee shield and carriage return

Hi, I have noticed a strange behaviour with my arduino mega. If I run this code:

void setup() {                
  Serial1.begin(9600);     
}

void loop() {
  Serial1.println("ottimost");
  delay(1000);              // wait for a second
}

I obtain on the terminal: ottimost ottimost ottimost ottimost ottimost

That's what expected. But if I run the same code with an xBee shield put on (using seral 0 not 1!) i obtain:

ottimost ottimost ottimost

ottimost ottimost

Sometimes there is a white line. It occurs not always at the same position... Any idea on the reason? Thanks!

hi, I have understood the problem is not concerning if xBee is present or not. The whites spaces appear if I use another serial monitor as coolTerm, never happen if I use the serial monitor included with arduino ide. Any idea about this behaviour?