Subdomain set but not working?

I am new to WPMU, I have created a site, and tried to create a new account, the wp-config has define('VHOST', 'yes');

It allows registration, sends the email but clicking on the link brings an error, the user is not in the users either.

First WPMU, first post.

You may test it here: http://www.instancesintime.com/

David