Got some cryptic message that "data in your calender has changed' and that I needed to deactivate and reactive the plugin.
Well, that really changed the data by wiping out all calendar data (there was a nice warning to back up). Don't really care about past calendar data though.
After reactivating...attempting to add a new event results in the really helpful error message, "Array". Can't wait to waste 3+ hours of my life trying to solve this problem/shop for a new calendar plugin.