Not sure what happened, but I went to add an new post the other day and I found the visual editor to be broken on my installation of WordPress 3.9.1 (at https://3z33.us)
I tried disabling all plugins, then enabling them one by one, with the same disappointing lack of effect on the visual editor.
I have tried posting a new post using Firefox and Chromium on Ubuntu Desktop, as well as Firefox and Chrome on Android, all with the same result.
I can still post plain text with hand typed html, but my installation doesn't really feel like it is running properly without the ability to upload pictures in the browser.
Any ideas on what could be causing this problem?