(X2e) HelloWorld => reboot Arduino !

Dear
I'm using HelloWorld.py (Digi example by socket) on a X2e Gateway. It's strange since the arduino reboot average 75% of each sent. I don't anderstand why ?
Here, the simple arduino code to read the data:

#include <XBee.h>

XBee xbee = XBee();
ZBRxResponse zbRx = ZBRxResponse();

void setup () {
delay(100);
Serial.begin(9600);
xbee.setSerial(Serial);
Serial.println("starting up yo!");
}

void loop () {
xbee.readPacket();
if (xbee.getResponse().isAvailable()) {
if (xbee.getResponse().getApiId() == ZB_RX_RESPONSE) {
xbee.getResponse().getZBRxResponse(zbRx);

Serial.println("Got an rx packet!");

if (zbRx.getOption() == ZB_PACKET_ACKNOWLEDGED)
Serial.println("packet acknowledged");
else
Serial.println("packet not acknowledged");

for (int i = 0; i < zbRx.getDataLength(); i++) {
Serial.print("payload [");
Serial.print(i, DEC);
Serial.print("] is ");
Serial.println(zbRx.getData(i));
}
}
}
}

Here HelloWorld.py from Digi:

import sys, os
import xbee
from socket import *

DESTINATION=("00:13:a2:00:40:d9:a7:b0!", 0xe8, 0xc105, 0x11)

Create the socket, datagram mode, proprietary transport:

sd = socket(AF_XBEE, SOCK_DGRAM, XBS_PROT_TRANSPORT)

Bind to endpoint 0xe8 (232):

sd.bind(("", 0xe8, 0, 0))

Send "Hello, World!" to the destination node, endpoint,

using the profile_id and cluster_id specified in

DESTINATION:

sd.sendto("Hello, World!", 0, DESTINATION)

Someone see whare is there the problem ?
Best regards.