I doubt it's XenForo related, but related to the way you have your HTTP server (or vhost) set up and re-writes that are in place. Is this a shared host, or a dedi/vps system (I see it's centOS so I am going to lean toward the latter).
I'm more a Debian guy, but if you want to start a convo with me I'll be happy to take a look at it and see if I can get it to working. The DNS resolves correctly so that's not going to be the problem.
Either a .htaccess rewrite, a hardcoded menu using an IP or you don't have the files uploaded to the right place are the most likely candidates.