After maybe an hour of getting extremely frustrated with this error that came up on the frontpage of my pretty new installation, I finally had a revelation and realized what was wrong.

You need to make sure that the domain you're accessing the Wiki through is setup in /etc/hosts (for Linux users).

So, if you're going to http://deki.brandnewwiki.blah, just make sure that the domain is in /etc/hosts

127.0.0.1 deki.brandnewwiki.blah deki

Just an example.

After I figured that out, everything started coming together and I can finally get busy with making use of the Wiki.

Keep up the good work, fellas!