Permalink Change Destroys Posts

Currently everything in my wordpress site is working fine. You can see it here: http://www.paynephotographystudio.com/photoblog/. I am using the default permalink structure.

I want to change it to %postname%. Once I do that, the main blog page looks fine, but when I click into individual posts, total destruction. The URL is showing correctly, but the content isn’t correct. It’s actually showing part of my homepage (all without the CSS).

I have no idea what’s going on here. Any help?