MediaWiki - 1.16.1 PHP - 5.4.24 MySQL - 5.5.36
My wiki (impdb.org) is posting this error when a new image is uploaded, and I have been searching like crazy for a couple of days and can not find a solution to this specific problem. The error is only viewable for persons who are logged in. If I (or other users) log out then the image thumbnail is viewable.