This class requires that you register for an additional class (generally a lab and/or clinical). You are unable to take a lab or lecture separate from each other. You will need to choose a lab and lecture section of the class and register for them at the same time. For certain courses, there is a specific lab assigned to a specific lecture class. You will find this information on the course schedule.
You may also be getting this error if you are registering for a lab and lecture at two different campuses. You must register for a lecture and lab on the same campus.