The post ID is already in the permalink, but that permalink doesn’t work. (e.g. you click the permalink and it loads up the /archives page) That’s the problem I’m trying to solve with mod_rewrite. (Because the problem appears to be caused by the default mod_rewrite settings that WP uses.)
Nevermind, it appears to have fixed itself!
Well, the brackets you don’t always need. I figured it out, though: I was missing some end quotes.
Thanks for the help, though! 🙂