Um, yeah. I probably should have mentioned that information. Might have been useful!
I am using 4.05.05
Core Events module 3.01.06
I figured out what the problem is. I have isolated it down to Locations. Here is how to reproduce:
a) Create an event and name itTest
i) Select a Category
ii) Don't select a location.
iii) Put in text for the description.;
iv) Click Update.
When you go to the list or month view and click on the event, my page just refreshes. It's the lack of location that seems to be throwing the error. Dunno if they fixed it in the version you have, but it's worth testing. I can't get rid of events I have created

I may have to delete the module and start anew. Let me know what your findings are.