xbee restarted !!!

Hello.
i have 2 xbee s2b and i configure one as coordinator and the other one as end point
i burn on the coordinator this code :

void setup()
{
Serial.begin(9600);
}
void loop()
{
Serial.println(‘H’);
delay(5000);
Serial.println(‘L’);
delay(5000);
}

and in the end point :
int led = 8;
void setup()
{
Serial.begin(9600);
pinMode(led,OUTPUT);
}
void loop()
{
if (Serial.available())
{
char incomingByte = Serial.read();

if (incomingByte == ‘L’)
{
digitalWrite(led,LOW);
Serial.println(“Turned OFF led”);
}
if (incomingByte == ‘H’)
{
digitalWrite(led,HIGH);
Serial.println("Turned on LED ");
}}}

the problem is :
the coordinator send to the End point H and the led turn on and write on the serial monitor that
then
after 5 sec the led is turned off but it doesn’t write in the serial monitor 'turned off led" and the arduino is restart
and start the program again.

can any one help me to found the error here please.
thanks