CMN ExchangeFreeBusyService log file shows contains error, "(401) Unauthorized." (4348097)

Notes users are unable to lookup free busy data for Exchange users. The Notes to Exchange free busy requests are making it past QCalCon and to the ExchangeFreeBusyService on the CMN Free Busy server. In the ExchangeFreeBusyService log file, the following errors can be seen:

2013-06-18 13:56:47,052 [22] ERROR ExchangeFreeBusyConnector - GetFreeBusyInfo()
Microsoft.Exchange.WebServices.Data.ServiceRequestException: The request failed. The remote server returned an error: (401) Unauthorized. ---> System.Net.WebException: The remote server returned an error: (401) Unauthorized.
   at System.Net.HttpWebRequest.GetResponse()
   at Microsoft.Exchange.WebServices.Data.ServiceRequestBase.Emit(HttpWebRequest& request)
   at Microsoft.Exchange.WebServices.Data.ServiceRequestBase.ValidateAndEmitRequest(HttpWebRequest& request)
   --- End of inner exception stack trace ---
   at Microsoft.Exchange.WebServices.Data.ServiceRequestBase.ValidateAndEmitRequest(HttpWebRequest& request)
   at Microsoft.Exchange.WebServices.Data.SimpleServiceRequestBase.InternalExecute()
   at Microsoft.Exchange.WebServices.Data.GetUserAvailabilityRequest.Execute()
   at QuestSoftware.CMX.API.Core.FreeBusyExchange.EwsHelper.GetUserAvailability(SmtpEmailList userEmailAddressList, DateTime startTime, DateTime endTime)
   at QuestSoftware.CMX.API.Core.FreeBusyExchange.ExchangeFreeBusyConnector.GetFreeBusyInfo(SmtpEmailList exchangeUserEmailAddressList, DateTime requestStartDateTime, DateTime requestEndDateTime)