Okay, "level 2" support said it wasn't their problem and I should try here--but I somehow still think it is the way the second domain is setup but here goes anyway.
I've previously had one domain (zaventh.com) running Mediawiki at http://www.zaventh.com/wiki . Now, I wanted to simply throw a new domain on top of that (nexuswiki.com) so that if you went to zaventh.com/wiki, it would be the exact same as nexuswiki.com/wiki. TCH parked the second domain for me, and I have it all setup as you would expect a domain should be.
Now, if one navigates to www.nexuswiki.com/wiki, it automatically rewrites the url to be pretty, and it should take you to http://www.nexuswiki.com/wiki/index.php/Main_Page, but it doesn't. Instead it takes you to http://www.zaventh.com/wiki/index.php/Main_Page. At first I thought perhaps the domain wasn't working right, but if you navigate to http://www.nexuswiki.com/wiki/index.php/Main_Page it works fine and as expected, except that if you save an edited page, it will redirect you back to the right page, but with the zaventh.com domain in place of nexuswiki.com.
My next and logical assumption was that it was using the domain name as a variable somewhere, but I couldn't see any obvious place to set it as it wasn't in the main config. So, I first search the entire mysql database, and there are 0 reference to either domain there. Next, I downloaded every file in the wiki and
>grep -i "zaventh" *.*
'd them all, and nothing came up. Nothing for the other domain either. This is what led me to believe somehow that nexuswiki.com was somehow resolving to zaventh.com, and when a redirect was called on the wiki, that is where it was going.
At any rate, if I would navigate to http://www.nexuswiki.com/index.php, it still wouldn't work right. The only thing between index.php and Main_Page is redirect.php. None of these files contain any actual domain names, but rather are used to rewrite the url I believe. I have attached these files, though I can't really see anything in them that would be causing the problem I am having.
Any help or ideas of where else to look would be great... Thanks.