Internal Server Error caused by protected domain h

Hi,

I got a problem: I did set up WP on a sub domain with domain protection via htaccess

AuthType Basic
AuthName „Login“
AuthUserFile .htpasswd
Require valid-user

Login is working fine.

After that

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /pr_blog/
RewriteRule ^index\.php$ – [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /pr_blog/index.php [L]
</IfModule>

and then I get a 500 Internal Server Error. When I remove the password protection, WP is running properly.