C# Outlook - Call Rejected By Callee

Trying to add an event to Outlook calendar through my event registration app using asp.net/C#. Getting call was rejected by callee error when trying to initialize (line 1). How do I overcome this issue?

Error: "Retrieving the COM class factory for component with CLSID {0006F03A-0000-0000-C000-000000000046} failed due to the following error: 80010001 Call was rejected by callee. (Exception from HRESULT: 0x80010001 (RPC_E_CALL_REJECTED))."

Outlook.Application outlookapp = new Outlook.Application();
Outlook.AppointmentItem appt = outlookapp.CreateItem(Outlook.OlItemType.olAppointmentItem) as Outlook.AppointmentItem;
appt.Subject = er.Event.Name;
appt.MeetingStatus = Outlook.OlMeetingStatus.olMeeting;
appt.Location = er.Event.LocationName;
appt.Start = er.Event.StartTime;
appt.End = er.Event.EndTime;
appt.Recipients.ResolveAll();
appt.Display(false);
appt.Save();

Firstly, you cannot use Outlook from a service (such as IIS).

Secondly, even if your code worked, you'd end up creating an appointment and displaying (!) it locally on the server machine, where there isn't anybody to see it.

Create an iCal file and provide a link to the user - the ics file will be opened on the client machine using Outlook and the user will be able to save it.