nginx goes down after creation of subdomains

Hello,

I provide web hosting with cPanel + Linux CentOs + PHP + MySQL + nginx

But usually when one of the users wants to create a subdomain the nginx goes down taking down all the websites of the server.

If I login as root and do:

/etc/init.d/nginx start

Starting nginx daemon: nginx nginx: [emerg] no host in ":80" of the "listen" directive in /etc/nginx/vhosts/subdomain.domain.com:3

I want to avoid all the websites down as result of one error in just one account.

Ideas?

Thank you