Fatal error: Call to undefined function wp_get_current_user() in /home/imnet/public_html/wp-includes/capabilities.php on line 1451
Secure WordPress is a plugin that I use on many of my other sites, and is one of the plugins that I usually recommend for securing WordPress. It seems however that plugin is not compatible with WordPress Multisite.
Thankfully it is easy to fix this problem by logging onto your server using FTP or your hosts file manager and deleting the SecureWordpress folder in the /wp-content/plugins directory. After doing that I refreshed the admin area of the site and it had started working again.
Now that I have discovered that Secure WordPress is incompatible with WordPress Multisite I will be looking at other options to secure my Wodpress Multisite set-up…