Views body field pop-up not loading and preview not working
This happened to me when I used the jQuery Update module with newer versions of jQuery (specifically 1.7). It causes several administrative oddities that you can get around, but the Views admin bug is pretty much crippling.

Here is a great patch that will allow you to choose a different version of jQuery for administrative pages, so for example, you can run jQuery 1.7 for the front end, but still use 1.4.4 for the administrative areas.

http://drupal.org/node/1524944