smush not working - cannot find images but images exist

I am trying to smush my images and it worked for the first 6,000 but now it is failing to find any images. When I double check in the browser the images exist.

This is the error:

Could not find /wp-content/uploads/2009/05/5-worst-presidential-candidates-who-lost1.jpg

Here's a link to that image: http://listverse.com/wp-content/uploads/2009/05/5-worst-presidential-candidates-who-lost1.jpg