OpenCV - waitKey(0) does not respond?

I'm using opencv 2.4.7 on ubuntu 12.04. I'm programming with python and I have a problem when i run this script:

import cv2

img = cv2.imread('347620923614738322_233985812.jpg')
cv2.namedWindow("window")
cv2.imshow("window", img)
cv2.waitKey(0)

The problem is that the script doesn't stop when I close the image. I searched information about waitKey and I found that using cv2.waitKey(0) is correct.

I don't understand, where is the problem?

This code works for me from IDLE:

# -*- coding: utf-8 -*-

# Objectif : découvrir le fonctionnement d'opencv-python
# http://opencv-python-tutroals.readthedocs.org/en/latest/index.html


import numpy as np
import cv2

# Load an color image in grayscale
img = cv2.imread('Lena.tiff',0)
WINDOW_NAME = 'Image de Lena'
cv2.namedWindow(WINDOW_NAME, cv2.CV_WINDOW_AUTOSIZE)
cv2.startWindowThread()

# Display an image
cv2.imshow(WINDOW_NAME,img)
cv2.waitKey(0) 


cv2.destroyAllWindows()

Hope this helps for future readers.