I had this issue after upgrading to 3.8.2 and determined (with the help of my hosting company) the the includes file, update.php needed to be restored. Once restored, my website is back online but I cannot access my admin page. Not sure what to do next. My website is https://www.lpmarcom.com
This is the error I receive:
Warning: require_once(/home/content/11/7981211/html/wp-admin/includes/update.php) [function.require-once]: failed to open stream: No such file or directory in /home/content/11/7981211/html/wp-admin/includes/admin.php on line 63
Fatal error: require_once() [function.require]: Failed opening required ‘/home/content/11/7981211/html/wp-admin/includes/update.php’ (include_path=’.:/usr/local/php5/lib/php’) in /home/content/11/7981211/html/wp-admin/includes/admin.php on line 63
