Kula9 on "Strange Fatal Error. Possibly permissions problem?"

Hey there,

I have very strange problem on my WP site:

You have the latest version of WordPress.
Fatal error: Call to undefined function request_filesystem_credentials() in /home/xxx/public_html/wp-admin/includes/class-wp-upgrader-skins.php on line 46

It started today, I tried to upload a file I am getting

Call to undefined function wp_handle_upload() in /home/xxx/public_html/wp-admin/includes/media.php on line 213

Its like something is missing in wp-admin folder. I tried reuploading wp-admin and wp-includes but no luck.

Any clues?