I upgraded our WordPress version to 4.0 this morning. When I tried to edit a page by adding new media, clicking on the “Add Media” button did not load the Media Library. I notice that a # was added to the full path name but otherwise there was no reaction by the system.
I emptied the cache and tried again to no avail.
I get the the same lack of response in both Chrome and Firefox browsers.
I’m not sure this is related, but I also don’t get the functionality described in the video wherein the toolbar remains visible when scrolling down through long texts on the page.