After removing a category, so that all courses where moved to the top category, the quiz/question module was broken for those courses who had changed level from a sub category to the top level.
When trying to add a new question(by clicking on question in the admin block in the course) we get the following message:
"This is an unknown context () in print_context_name!"
and are then being redirected to the frontpage.
Making a backup of the course and restoring it to a new course solves the problem.