The weird part about having to go back and add in the Joomla Superuser account as an explicit user with all the permissions enabled was that JEvents 2 did work fine right out of the box with Joomla 1.7, allowing creation of a couple of events.
Nonetheless, adding the Superuser as a user with all permissions enabled did get me back to being able to add events as I happened to be working as Superuser.
I'm guessing that the ability to add events changed after I (as Superuser) added and enabled some new user accounts to test the usual case in which people who add events do not have Superuser permissions. At least this seemed to be the timing of when the 403 displays occurred when trying to create events. At that point I was still able (as Superuser) to create and edit calendars and categories, just not events.
This was on a Windows development system, BTW.
Seems like a really nice extension that deals with iCal so it's probably worth learning a couple of quirks to get so much functionality. Thanks.