JS-Error in ms-admin.js

I just installed Protected Content. When I tried to protect a page (on the page-edit screen), I did not see the nice »Membership Access« box. So I tried to change my screen-settings, but unfortunately the toggle to slide down my screen-settings did not work. I checked the console and it reported:

Uncaught TypeError: undefined is not a function – ms-admin.js:69

Am I the only one with that problem?

Thanks for your help!