I've had several images disappear from my blog (little red X). When I go to edit the entry, the image appears in Visual (and the HTML code is there), but when I View the site it is not there. The link to the image also works fine. I tried deleting and replacing. This all started yesterday when there were changes made to the editor.
The only workaround is to rename the image on your computer, reupload the renamed image, and then insert it back into the blog (or you can change just the filename in the HTML if you don't want to wrestle with all the reformatting issues going on). Needless to say, this with all the other problems with the alignment, makes for a very frustrating experience.