So I have a new installation of Xenforo, and I'm getting 404 errors on all of the actual forum threads; doesn't matter what forum it's in. The forum link itself works, and I can drill down and see the post itself, but when I try to access it, I get the requested page not found.
There are no errors in the ACP, but I can clearly see a 404 error in the Apache error log for the site. Of course, the first thing you think of is mod_rewrite, but it's properly configured and working for all other sites on the server. I've tried it with the htaccess, without the htaccess, trying it with and without the friendly URLs (it still happens without the friendly URLs, which to me points to a non-rewrite issue), and it still doesn't work.
Note that this is a new forum install, and I didn't discover this until well after I'd installed the theme, some addons, and so forth. So I'm not sure if it was ever working. This also seems to be the only thing not working, although it's obviously a big one. Am running it behind CloudFlare, but putting it in development mode to disable caching and clearing my own cache doesn't help.
Xenforo Version: 1.5.x
Addons: Really too many to list, but nothing affecting forum threads.
Example Forum URL: http://minestyria.com/forums/announcements/
Example Thread 404: http://minestyria.com/threads/forum-rules.1/
Am a Linux administrator, so no need to dumb anything down for me. I really do believe it's rooted in my settings somewhere, rather than the actual OS or Apache, since everything else on the server is running fine, and I make liberal use of mod_rewrite throughout (I *am* using the default htaccess for Xenforo).