I just installed W3 Total Cache, and TinyMCE stopped working. I can't switch to the visual editor to edit pages or posts. I assumed Minify was the problem, and turned off Minify. Then I cleared the cache, as well as my browser cache, but TinyMCE still wasn't working.
Then I loaded another browser, and TinyMCE still isn't working. I disabled the W3 Total Cache plugin, and TinyMCE still isn't working. That is the only change I've made to my site recently. I re-uploaded a backup of my site, and it is still broken.
And it looks like someone else had a very similar problem with this plugin before: