Last night, everything was working just fine. But this morning, as I logged into my Dashboard to add a new link to my menu, I noticed the Menu link under Appearance had completely vanished without a trace.
I have tried accessing it by typing addresses such as: http://mysite.com/wp-admin/nav-menu.php and http://mysite.com/wp-admin/menu.php into my address bar and both pages alternate between a 404 page and a white page with the following message:
Fatal error: Call to undefined function __() in /home/user/public_html/wp-admin/menu.php on line 25
I have not made any changes to my theme, installed new plugins, or anything like that since I last logged out and I've checked my functions.php file and it has the required code to generate a menu.
Any ideas on what could've happened and what I need to do to get it back?
PS. I am using WordPress 3.8 and I have tried accessing the Dashboard from different browsers and I am still experiencing the issue.