I now use this setup and it works. Don't ask me why...
<Directory /var/www/karstenj/stories/dev>
allow from all
Options +Indexes
</Directory>
RewriteEngine On
RewriteRule !(^/design|^/var/.*/storage|^/var/storage|^/var/.*/cache|^/var/cache|^/extension/.*/design|^/kernel/setup/packages|^/packages|^/share/icons).*\.(gif|css|jpg|png|jar|js|ico|pdf|swf|html)$ /index.php