I just tested the insert page and uploaded three images and both the thumbnail and image were uploaded with increments to the server. I'm looking in the upload folder and I can see it has worked for you several times in the past as well. Maybe it just isn't working in certain circumstances? Maybe it is a problem on the update page? I'm going to need more information in order to reproduce the problem before I can tell you why it happens. What steps are you following when you see this issue? Maybe it has something to do with the image you are uploading?