I had a similar problem.
I got blank shots when I tried to capture pictures from googleusercontent.com (strange!). Then I had to reboot in order to have ScreenShot Captor working properly.
I think (and hope) that I solved the problem permanently by changing the settings of Zone Alarm Extreme Security (from ?, ?, ?, ?, ? to II, v, v, v, v -> see the attached picture)
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