After upgrading WP up to 3.6.1 right sidebar from admin's widget menu disapeared. It's means widgets work OK on site (You can see here) but I cannot change/ edit them from admin menu. Also buttons "screen option" and "help" are not work as well.
My WP 3.6.1, Twenty Ten version 1.6. Multisite (Network). I use Child theme. In child theme folder only 4 files: footer.php, style.css, functions.php, header.php.
Any ideas what I can do?