WordPress3.4にアップデートで管理画面に入れない

本日、3.4にアップデートしたら管理画面に入れない状態になりました。
プラグインはFTPで全て削除、wp-content/db.phpも削除しました。3.4のzipファイルをダウンロードしてFTPでアップしても同じです。

出ているエラーは下記のとおりです。
WordPressはマルチサイトで運用していて、サーバーはエックスサーバーです。
ご教授よろしくお願いします。

Notice: convert_to_screen(), add_meta_box() が誤って呼び出されました。Likely direct inclusion of wp-admin/includes/template.php in order to use add_meta_box(). This is very wrong. Hook the add_meta_box() call into the add_meta_boxes action instead. 詳細は WordPress のデバッグをご覧ください。 (このメッセージはバージョン 3.3 で追加されました) in /home/vanguard/kaibundou.com/public_html/wp-includes/functions.php on line 2825

Warning: Cannot modify header information – headers already sent by (output started at /home/vanguard/kaibundou.com/public_html/wp-includes/functions.php:2825) in /home/vanguard/kaibundou.com/public_html/wp-login.php on line 365

Warning: Cannot modify header information – headers already sent by (output started at /home/vanguard/kaibundou.com/public_html/wp-includes/functions.php:2825) in /home/vanguard/kaibundou.com/public_html/wp-login.php on line 377

Warning: Cannot modify header information – headers already sent by (output started at /home/vanguard/kaibundou.com/public_html/wp-includes/functions.php:2825) in /home/vanguard/kaibundou.com/public_html/wp-includes/pluggable.php on line 680

Warning: Cannot modify header information – headers already sent by (output started at /home/vanguard/kaibundou.com/public_html/wp-includes/functions.php:2825) in /home/vanguard/kaibundou.com/public_html/wp-includes/pluggable.php on line 681

Warning: Cannot modify header information – headers already sent by (output started at /home/vanguard/kaibundou.com/public_html/wp-includes/functions.php:2825) in /home/vanguard/kaibundou.com/public_html/wp-includes/pluggable.php on line 682

Warning: Cannot modify header information – headers already sent by (output started at /home/vanguard/kaibundou.com/public_html/wp-includes/functions.php:2825) in /home/vanguard/kaibundou.com/public_html/wp-includes/pluggable.php on line 881