Rather than dealing with my .htaccess problems to fix the error, I thought this would be a better approach: http://wwdj.wijndaele.com/getting-started-with-cakephp-without-mod_rewrite/
Unfortunately, it messed up quite a few links on my site.
I ended up solving the problem by changing "AllowOverride" None to "AllowOverride All" in my /etc/apache2/sites-available/default file.
Why the heck is CakePHP using .htaccess files by default anyway? Yii has this more streamlined.