Was this ever solved? I am having the same issue. I have installed over a dozen blogs since Christmas and this is the first one that I am getting the error on. I think it is because I imported the posts and media from a previous blog – we were just moving the blog to a new server.
When we go to add an image or media to a post or page, we get the pop up window that says: Are you sure you want to do this?
Please try again.
When I click ‘please try again’ is loads the wp admin dashboard again within that window.
When I go to the media tab and upload an image directly that way, I don’t get this issue.