Python# screenshot failure

I am using PIL(Python Imagi开发者_高级运维ng Library) for grabbing the image. But grabber() throws the following error message if I minimized the window

img=ImageGrab.grab()
File "C:\Python26\lib\site-packages\PIL\ImageGrab.py", line 47, in grab
    size, data = grabber()
IOError: screen grab failed

My browser shot factory is installed in a Win 2003 Server in a VM. I am doing a remote desktop to view the browser shot factory's console.

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There is a very similar question located here - it even has some alternatives and solutions, and (as Adam Bernier has written), imagegrab works only on Windows.