Content Type locked?

I have just finished creating a training course using the "Course Presentation" content type. For some reason I can now only see the first slide in the Edit tab and the View tab doesn't display this first slide. The 'Content Type' field has become locked and the options below the window no longer display. I've uploaded two screenshots below, the first one is it looking correct for another course and the second is how it looks for this one. Hopefully it will have just been me accidentally clicking something! Any help is appreciated.