WP Multisite Subdomain ERR_TOO_MANY_REDIRECTS

Hi!

We have a fresh WP in our subdomain development.mydomain.com. We already have an existing WP installation running on http://www.mydomain.com (not multiuser). So we followed the http://codex.wordpress.org/Create_A_Network. After we did all settings everything is working fine for development.mydomain.com, but when we create a new site (for example development.mydomain.com/test) and want to acess this site it looks strange -> looks like css isn’t loaded. And when we access the admin pane (for example development.mydomain.com/test/wp-admin) we get ERR_TOO_MANY_REDIRECTS.

Our .htaccess looks like this:

RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]

# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(wp-(content|admin|includes).*) home3/www/mydomain/_development/$2 [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(.*\.php)$ home3/www/mydomain/_development/$2 [L]
RewriteRule . index.php [L]
</IfModule>

Our wp-config.php looks like this:

/* Multisite */
define('WP_ALLOW_MULTISITE', true);
define('MULTISITE', true);
define('SUBDOMAIN_INSTALL', false);
define('DOMAIN_CURRENT_SITE', 'development.mydomain.at');
define('PATH_CURRENT_SITE', '/');
define('SITE_ID_CURRENT_SITE', 1);
define('BLOG_ID_CURRENT_SITE', 1);