Featured Image Not Working

I am using the Mystique theme with Featured Images, and they’ve worked like a charm. However, now whenever I try to select the little star to feature the image it doesn’t work… and when I go back to my Media Library the image isn’t selected as featured.

I select it again, and once more it doesn’t work… and when I go back to my Media Library the image isn’t selected as featured.

Please assist.

site: tristanbills.com