the only thing I can see from this screenshot is that there's no user selected for Event Owner. In my Event properties, the Event Owner is populated with a name when I pull it up. If yours says Select User, I'd be suspicious that the user you've chosen as owner isn't sticking (which would make sense if you're unable to make these changes to the event).
Also, and this is just brainstorming out loud, is it possible there's another event that overlaps in time/date and the overlap check isn't turned off? It's abit of a stretch, but it's best to rule out everything we can...
Norm, there is no problem with your X or check. One will never show on the end date. There is ONE validation for the date/time settings as a whole which checks things like making sure the end date/time is AFTER the start/date and time. So there is no issue that is seen in your screenshot. Submit a ticket and we'll check it out. Be sure to include what browser you are using. Maybe that is related.
Firstly, in Google Chrome not all X were being shown.
When I tried it in FF, I discovered that the "Minimum Group Size" was defaulting to 0 (I hadn't set it)... and needs to be 2.
Thank you for your help... might want to check this out.