Widgets page nonfunctional in 4.5.1

Hi –
Ive seen this on two of my sites now using both FF and Chrome.
The current widgets wont move or expand.
New widgets cannot be added.

Here is a quick video demo of the problem.
https://screencast.com/t/zqaq6fyiAn

Note: I will make a separate post about the admin menu behavior that also appeared at the same time on both sites.