Thumbnails Disappear When I Publish

I’ve taken this problem to the NexGen forum and gotten no response. I’m hoping someone here can help.

When I insert singlepics from my NexGen gallery in a post, they show up beautifully when I save as a draft. But as soon as I publish, the singlepics get stripped out and replaced by ugly white tabs. Here’s an example: http://stormhorn.com/2010/12/18/for-the-birds/

The tabs are active; you can click on them and still get a full-size image.

I recently switched Web hosts and in the process I had the person who moved my files (a friend and admin for my former host, which was ceasing operation) move WP to the root directory of the new host. For the most part things seem to work, though I’ve had to fix some broken links and rewire incorrect ones), but this problem has been a pain in the butt, and I’m not sure it’s due to the move. WP had an upgrade at about the same time; NexGen also upgraded a couple times in that same time period, and it appears that lots of people have had thumbnail issues. The NexGen forum hasn’t been responsive; maybe someone here can help. I hope so–I’ve got over 400 images in my gallery.

Maybe someone here can help.