Images on WP Pages breaking layout

I am having a weird issue with image content on WP pages that I’m not being able to replicate locally. Here’s a picture for better understanding:

http://dl.dropbox.com/u/1354385/dd_wpissue.png

Basically, I add an image to the page content, like so:

http://dl.dropbox.com/u/1354385/wp-addingimage.png

And then the image somehow “leaks” into the header, breaking the layout.

I run WP locally on MAMP having the same version and plugins, and I can’t replicate this issue. This is happening on the live site (It’s a webcomic using Comicpress and a custom child theme).

http://www.daledani.com/info/

Any help much appreciated on this. Thanks!