Thanks for that, I got it working again.
I also managed to re- create part of my previous problem, I think. What I did was to create an event in the past, which worked, but the end date turned out to be the present. So I went back in and changed the end date to the same day as the event. The event then disappeared off the events manager. It is still there on the calendar view, displaying a 1 day event that was in the past.
I think what I did previously was to try to re-create the disappeared event in the event manager (possibly with the same name), which maybe confused something causing all but one event to disappear off the calendar view.
I realize trying to create events in the past may be stupid, but I was trying to set up a demo.