I tried deactivating all plug-ins. This is on a multi-site setup and on the base site, it works. On the added sites, I get no image when I add a caption to it.
If I view source, the image is there, it just doesn't display.
<div class="wp-caption alignnone" style="width: 283px"><img class=" " src="http://allsafepestprevention.com/files/2011/06/iStock_000011690439XSmall117.jpg" alt="" width="283" height="424" /><p class="wp-caption-text"><span>A Mosquito - Magnified</span></p></div>
Here is the post where it does display