3821807 - Why do I receive an Application Error when trying to create a new Attendee Type?

When I try to create a new Attendee Type I receive an application error: Unexpected System Error. Please try your action one more time. If you encounter the error again, please forward all information, including the events leading to the system error, to your Expense Administrator.

When trying to add a new attendee type, I receive an application error with a spinning wheel. Internal error: SQLServerException: Violation of UNIQUE KEY constraint 'UK_CT_ATTENDEE_TYPE_LANG'. Cannot insert duplicate key in object 'dbo.CT_ATTENDEE_TYPE_LANG'. , KBA , CON-EXP-ADM-ATN , Attendees , CON-EXP-EXP , Expenses , Problem