How to fix links on website that do not work?

We have a multisite enabled WordPress install. The front page works however when you click through links. The result is a 404 Not Found error.

Not Found

The requested URL /manage/ was not found on this server.

Our .htaccess is

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

# add a trailing slash to /wp-admin
RewriteRule ^wp-admin$ wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d

RewriteRule ^ - [L]
RewriteRule ^(wp-(content|admin|includes).*) $1 [L]
RewriteRule ^(.*\.php)$ $1 [L]
RewriteRule . index.php [L]
#RewriteRule ^(.*)$ index.php [L]

Can you please help?

You can check it out on http://ezisites.com/plus/