A Single Post Causing Problems

I’ve got a single post on my site that’s causing problems and I can’t figure out why.

I’ve configured the menu bar of the site to include a few category items rather than have them in a sidebar widget.

Viewing any page or article except this one everything works as it should. The dropdown menus work properly and navigating to any other area of the site works fine. With this one particular article; however, you’ll see that the arrows in the two dropdown menus are gone. Clicking on any menu item or on the main link at the top of the page generates a 406 Not Acceptable error.

I’ve Googled and most of what I found says it has to do with something about mod_security. I don’t entirely know what that is but it sounds like it’s something that my host puts in place. As far as I’ve read I can disable it in the .htaccess file but doing so reduces security on my site.

Why would it affect a single post/page and not all? What actually is the issue? How can it be resolved?

Thanks.