Plugin kills Media Library and Editing

I upgraded to 4.5.1. I tried to upload images to the Media Library, but it was greyed-out and did not show the assets. I could not add media in a post, nor could I edit the URL or switch to “text” edit.

I deactivated all my plugins and then turned them on one-by-one and tested the Media Library. It all worked fine until I hit this one. I tried it off and on a few times just to be sure. I was sure.

If you suddenly experience problems with your Media Library or editing functions, this might be the answer. Several forum posts suggested deactivating plugins and several suggested other things. This worked for me. Hope this helps some poor frustrated WordPress user out there! Thank you.