Can't type in 4.2.1 on mac

I am running 4.2.1 and am suddenly unable to type a new post; i.e. the page loads fine, but the text box is unclickable. I am running a MBP with OSX 10.10.3 However, my administrator is able to type up a post just fine with her Windows 7 machine.

Any ideas? It’s obviously not a plugin interfering if one of us can type, but I’m stumped.