I really need some help on this one, because I have absolutely no idea what's going on here. At first, I was cleaning my database with 'Optimize DB' plugin. The plugin frooze in my parent blog (usually there is a checking database now message, then show the cleanup records), so I went ahead and deactivate the plugin and deleted it.
Then, I visited one of my child blogs and this error message showed up.
Fatal error: Call to undefined function wp_get_current_user()
I saw a solution to insert 'require_once('pluggable.php');' line right after <?php in capabilities.php. I go ahead an did that, but now I'm getting this Fatal Error:
Fatal error: Call to undefined function get_current_screen()