C# – receiving exception from Office’s Outlook library

I have an application that calls

Email hello = new Email(appropriate constructor);
hello.Email_Send();

I'm receiving the exception:

Retrieving the COM class factory for component with CLSID {0006F03A-0000-0000-C000-000000000046} failed due to the following error: 80080005 Server execution failed (Exception from HRESULT: 0x80080005 (CO_E_SERVER_EXEC_FAILURE)).

from System.Runtime.InteropServices.COMException.

using O = Microsoft.Office.Interop.Outlook;    
class Email
{
    public void Email_Send()
    {
        O.Application outlook = new O.Application(); //Exception thrown here.
        O.MailItem message = outlook.CreateItem(O.OlItemType.olMailItem);
        message.To = Receiver;
        message.CC = Sender;
        message.Subject = Subject;
        message.Body = "This is an automated message sent at " + DateTime.Now.ToString("HH:mm:ss") + " about " + Body_Topic + System.Environment.NewLine + Body_Content ;
        message.Send();
    }
}

This error has never happened previously, and there has been no change to the code that I know of. http://support.microsoft.com/kb/825118 doesn't seem to fit the my symptoms – My computer doesn't stop responding, etc.
Any help diagnosing the issue would be greatly appreciated!