Post Editor Link Buttons Disabled since 4.0

After upgrading several sites I manage to WordPress 4.0, all sites no longer have ability to use the link buttons in the visual editor. I’ve tried flushing Cloudflare and browser caches, disabled TinyMCE plugins, disabled Page Builder / similar plugins, and still not working on any of 4 different installations.

I also tried a clean-install from my host’s one click setup, and I still cannot click those darn buttons. This install has no plugins or themes other than what comes out of the box.

Hosting on MediaTemple grid. Thanks in advance for the help!