Internet explorer screen shot has content black on windows 2008 R2

Hi 

Am taking the screenshot of the opened internet explorer (ie9) window on windows 2008 R2 using 

Win32.PrintWindow(wndHWND, capHDC, 0);

But at times the page appears black, even though the page has content

link to the image

I am opening multiple IE windows , could the overlapping be an issue ?

Thanks

Ananya Saxena