cv2 imshow command doesn t work properly in opencv-python

Question

I'm using opencv 2.4.2, python 2.7 The following simple code created a window of the correct name, but its content is just blank and doesn't show the image:

import cv2
img=cv2.imread('C:/Python27/03323_HD.jpg')
cv2.imshow('ImageWindow',img)

does anyone knows about this issue?