kitchen sink gone after update

After updating WP, the kitchen sink is gone. I’ve tried:
– deactivating all plugins (no luck)
– switching to Twenty Eleven (no luck)
– setting the Permalinks to default (no luck)
– see what Firebug has to say. Maybe some luck there?
“NetworkError: 404 Not Found – https://updatetest.casinogokken.net/wp-includes/js/tinymce/langs/nl.js?ver=349-20805”
nl.js?…9-20805
Failed to load: https://updatetest.casinogokken.net/wp-includes/js/tinymce/langs/nl.js
wp-tin…9-20805 (regel 1)
“NetworkError: 404 Not Found – https://updatetest.casinogokken.net/wp-includes/js/tinymce/themes/advanced/langs/nl.js?ver=349-20805”
nl.js?…9-20805
Failed to load: https://updatetest.casinogokken.net/wp-includes/js/tinymce/themes/advanced/langs/nl.js
wp-tin…9-20805 (regel 1)”

So I added these files in said locations, then checked in the browser if these files could be found, and then checked the kitchen sink again, but it is still gone, and the errors remain the same.