This issue was caused by a custom data list.  The custom events data list existed in the original version of the database, but when the database was upgraded, the custom data list was not loaded into the new environment.  This specific situation was resolved by loading the data list from the original version of the database.

This issue was caused by a customization. If you are experiencing a similar issue, review How to request assistance for customization issues in Blackbaud CRM for more information.