Problem with wordpress 3: Call to undefined function is_site_admin() and plugin doesn`t work

i'm a new one at wpmudev. I've installed worpdress 3, enabled multisite, upload correctly update-notifications.php file from rebranding-wordpress-mu, but when i`m trying to login into admin panel i receive an error: "Fatal error: Call to undefined function is_site_admin() in /wp-content/mu-plugins/update-notifications.php on line 417"

Please tell me what is wrong with that file?

The second: uploaded into mu-plugins file login-image\login-image.php from "rebranding wordpress" doesn`t work. i mean there is NO additional options into admin panel to change images - why?