I've had the same problem, everything non-configured by virtualmin showed up the first domain I did configure, but I've added this to my /etc/httpd/conf/httpd.conf file at the section where all the Vhosts were :
Code:
<VirtualHost xx.xx.xx.xx:80>
DocumentRoot /var/www/html
<Directory /var/www/html>
Options Indexes IncludesNOEXEC FollowSymLinks
allow from all
AllowOverride All
</Directory>
</VirtualHost>
Now it shows up as empty (since /var/www/html is empty too), could also post a message there or whatever.
I'm on CentOS btw, so the config might differ.