Can't acces dashboard nor site in multisite subdomain installation

In installed a new instance of WP and followed all points from the multisite instrution in the codex.

I updated wp-config.php and .htaccess accordingly and setup a * A record in my DNS. My provider supports wildcard subdomains.

I can now create new sites without a problem, getting all the registration emails and stuff. But when I try to access the subdomain it does not work. subdomain.domain.com only shows a generic page telling me that the site is temporaly down (this happens for any subdomain). wp-admin/ is not accesible and shows this:

“The requested URL /wp-admin was not found on this server.”

What could be the reason for this problem? Thanks in advance!