Unable to install 2.6.2 -- URL Redirect Issue

Moodle 2.6.2. Or trying to, at least.

I've placed my code in my subdomain:

http://gorwanda.ucdavisextension-onlinelearning.net

But when I try to install Moodle, I get an error telling me that the site is available only through the main domain. I'm baffled because...

1. I've installed Moodle 2.6.2 in several other subdomains without this problem;
2. There is no config.php file (remember, I haven't been able to even get to the install scripts at this point);
3. There is no .htaccess file; and
4. The configuration of this subdomain on my webserver is the same as every other subdomain.

What am I missing here?