After I click the "Okay, these look good..." it slides across and it's just a white box with "Post Thumbnail Editor" as the title. Tried it a couple of times and same problem. So I can't actually modify the images. Using Firefox 5 and WP 3.2.1.
Also I noticed when I was using an earlier version of your plugin, you could edit the images after you click on "edit image" button. It used to be on the right hand side underneath the image cropping that wordpress provides. Is this no longer the case? Is the only way to get to it from the media screen and by clicking the "thumbnails" link? I ask because I have disabled the media library for my users on this particular site and now I don't think they have any way to edit their images :)