The widgets page on one of my WP sites has stopped functioning. I can't edit, add, delete, or even drag elements on the page. When I click on the arrow on any installed widget, the page jumps slightly and momentarily, but that is the only response I get on the page. I've done everything I can think of. I disabled all plugins even though I hadn't added any recently. I removed the widgetizing code from header.php completely and the widgets are still there. I've updated to the most recent versions of WP and Atahualpa. I've run WP Security Scan as well as having the server scanned, and nothing malicious shows up. I've thoroughly read every line of code on any page that might relate, and can't find an obvious glitch. I'm baffled, any ideas?
Thanks in advance.