Fatal error: Call to undefined function

I’m suddenly locked out of my site. I was there doing a post, and everything was fine. Finished my post, closed out site. Next thing I know, client calls to let me know the site is inaccessible.

The error I see is:

Fatal error: Call to undefined function wp() in /home/XXXXX/public_html/wp-blog-header.php on line 16 on my main page.

That line of code is

// Set up the WordPress query.
	wp()

I’m also locked out of the admin panel…

Fatal error: Call to undefined function nocache_headers() in /home/XXXXX/public_html/wp-admin/admin.php on line 33'

and that code is…

require_once(dirname(dirname(__FILE__)) . '/wp-load.php');

nocache_headers();'

I do use InfiniteWP to keep track of all my sites. It shows it updated Better WP Security and UpDraftPlus. I don’t even know what UpDraftPlus is. I don’t think Better WP was active, though I may be wrong there.

Other plugins:
W3 Total Cache
Contact Form 7
Custom Facebook Feed
Wordpress SEO
WPSEO Local

I tried to disable those plugins, and it didn’t help the issue.

Anyone have any ideas?