bartvanlieshout

I fount the answer. It is in the css of the admin.
open wp-admin/css/wp-admin.css and search fot the first instance of “screen-option-wrap”. follow the text a little further until where it says “{visibility:hidden}” change “hidden” into your first name and save the file. Both widgets, screen-options and other non-working elements seem to perform perfectly!

Yes I tried already that, reinstall via download and also via the backoffice itself, using the update option. I suspect is has something to do with the webserver (MAMP), since the problem is only with some behavior that seems to be javascript related.