If you have upgraded to the latest WordPress v3.7, you may meet the image caption problem in the visual editor, this is a particularly nasty bug that affects working with image captions in the visual editor. It was caused by a regression in Uglify.js.
New captioned image inserted into the Visual Editor produces a huge data-mce-style width (10000px+) moving the inserted image out of the editor viewable area.
The problem will be fixed in the next version V3.7.1, If you don’t want to wait for the auto-update, you can download the following tinymce folder, unzip it and replace your old tinymce folder.
I have tested it and it worked.
Download the tinymce
don’t forget to refresh the browser cache.