In the process of disabling some slightly used plugins, slaptijack.com got into a situation where every permalink simply pulled up the home page rather than individual posts. I checked everything (mod_rewrite in my Apache configuration file, changes to .htaccess, etc.), but nothing fixed the problem.
I use a custom permalink structure on this site. In the end, the fix to my problem was to reset the site permalinks to default and then set them back to my custom structure. Magically, everything started working.