I've been trying to troubleshoot this on my own for over 2 hours now and none of the fixes seem to work.
If you visit http://www.getmightynow.com and click the "articles" parent category, it goes to a blank directory listing. It's weird that the parent link is broken, but the child category links work just fine.
mod_rewrite is enabled on hostmonster by default, so it's not that
I did the .htaccess file reset by disabling all plugins, deleting the .htaccess file, resetting my permalinks and then trying the link (still broken), and then re-enabled my plugins since those weren't the problem
I'm using WordPress 3.4.2 and all plugins are up to date.
Any other ideas?