Fatal error: call to undefined function

I attempted to update automatically to 3.1.1 and received the error code Fatal error: Call to undefined function is_network_admin() in /home/pgharts/public_html/wp-admin/admin-header.php on line 16 when logging into dashboard.

I then manually updated to 3.1.1. I then received the error code of

Fatal error: Call to undefined function is_network_admin() in /home/pgharts/public_html/wp-admin/includes/menu.php on line 10menu.php on line 10 when logging into dashboard.

there is a file called menu.php in
/home/pgharts/public_html/wp-admin/includes/

What to do???

Thank you!