Multisite .htaccess error? CSS broken and infinite loop on wp-admin

I just did a new install (WP 3.7.1) and enabled the multisite using subfolders like I allways did.. and the result was that on the new sites (except main) the css/js links to the theme were broken. And the dashboard for the subsites domain.com/dummy-site/wp-admin/ caused an infinite loop.
The problem were these two lines in the .htaccess:

[...]
RewriteRule ^([_0-9a-zA-Z-]+/)?(wp-(content|admin|includes).*) $2 [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(.*\.php)$ $2 [L]
[...]

I checked another working multisite of mine and found that the .htaccess was different, I replaced then the above two lines with the old ones and now everything is working like it should:

[...]
RewriteRule  ^[_0-9a-zA-Z-]+/(wp-(content|admin|includes).*) $1 [L]
RewriteRule  ^[_0-9a-zA-Z-]+/(.*\.php)$ $1 [L]
[...]

Any idea on what is wrong with the new .htaccess in WP 3.7.1 ??