psylem

Seems like “Visitor Like/Dislike Post Rating” plugin was the culprit in my case. Disabling that plugin has fixed my WYSIWYG editor and the jQuery javascript error is gone.

Although, I did firstly try replacing wp-admin and wp-includes directories to no avail. I don’t think that contributed to the fix.

a) dashboard

I think I may have the same problem as you. I’ve updated and now I can’t edit my post. I get a heap of javascript errors and can’t click on any of the WYSIWYG controls. I can’t click the HTML tab either, I get “switchEditors is undefined” javascript error in the log.

Luckily I have a WP client on my phone, so I was able to clear up those embarrassing grammar issues in the nick of time with that.