So I’m having the same problems here. I’ve disabled all plugins and flushed all caches on the browser. Went back to a page to add an image, clicked the media button, got the UI to pop open the lightbox (bad choice of UI for this interaction by the way guys)…dragged my image in there, and it uploaded and inserted into the page fine. Updated the published page. Went back to the page to add another image, now the UI is broken. Clicking the add media button no longer works. NOTHING has changed other than what I did above. This is a HUGE problem and I hope to God someone is coding hard and furious right now…I’d set this as a P0 bug.
