Cannot trash certain events

Hi,

I'm having problems deleting some particular events and categories. When I try to delete the categories, I'm told I need to delete the associated events first, which I'm guessing is the intended behavior.

When I try to delete the events themselves, however, I get the message "870 -It was not possible to delete this event".
If I try to edit the same events, I get "403 You are not authorized to view this resource/perform this task."

I'm logged in as Super-User for the site.
I've tested by creating other events, and I'm able to edit/delete these just fine.

This is a new page that is only just set up. The installation is based on a quick start template, and it had an extra user, which I promptly deleted. I suspect that's the reason for my woes, but as SuperUser, I should be able to edit/delete things as I please, right?

Is there any way to fix this, short of going into the database and deleting the corresponding rows? If this is what I have to do, which tables do I need to check?