Okay, after visiting your forum that answer is simple. I thought we had this worked out last time, but:
You have your wiki URL at a sub-domain that is different from your forum. There are bugs in vBulletin, especially in the editor, which make this impossible, even though they claim to allow it for blogs and CMS. There are a lot of people complaining about this on their site, and they are resistant to finish the fixes they already started. Unfortunately we can't do anything about this, because we don't have control over the core vBulletin files.
In order to have a functional wiki, it will need to use your forum sub-domain until they work their stuff out.