Exchange 2013 MSExchange Certificate Notification Error 2001

I literally have no idea of what to do with this error. I only see it when I restart the our Exchange 2013 Front End server.

Log Name:      Application
Source:        MSExchange Certificate Notification
Date:          9/20/2013 2:28:46 PM
Event ID:      2001
Task Category: General
Level:         Error
Keywords:      Classic
User:          N/A
Computer:      front end server
Description:
A transient failure has occurred. The problem may resolve itself. Diagnostic information:

Microsoft.Exchange.Data.DataSourceOperationException: The request failed. The remote server returned an error: (401) Unauthorized. ---> 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.EwsHttpWebRequest.Microsoft.Exchange.WebServices.Data.IEwsHttpWebRequest.GetResponse()
   at Microsoft.Exchange.WebServices.Data.ServiceRequestBase.GetEwsHttpWebResponse(IEwsHttpWebRequest request)
   --- End of inner exception stack trace ---
   at Microsoft.Exchange.WebServices.Data.ServiceRequestBase.GetEwsHttpWebResponse(IEwsHttpWebRequest request)
   at Microsoft.Exchange.WebServices.Data.ServiceRequestBase.ValidateAndEmitRequest(IEwsHttpWebRequest& request)
   at Microsoft.Exchange.WebServices.Data.ExchangeService.InternalFindFolders(IEnumerable`1 parentFolderIds, SearchFilter searchFilter, FolderView view, ServiceErrorHandling errorHandlingMode)
   at Microsoft.Exchange.WebServices.Data.ExchangeService.FindFolders(FolderId parentFolderId, SearchFilter searchFilter, FolderView view)
   at Microsoft.Exchange.Data.Storage.Management.EwsStoreDataProvider.InvokeServiceCall[T](Func`1 callback)
   --- End of inner exception stack trace ---
   at Microsoft.Exchange.Data.Storage.Management.EwsStoreDataProvider.InvokeServiceCall[T](Func`1 callback)
   at Microsoft.Exchange.Data.Storage.Management.EwsStoreDataProvider.GetOrCreateFolderCore(String folderName, FolderId parentFolder, Func`1 creator)
   at Microsoft.Exchange.Data.Storage.Management.AsyncOperationNotificationDataProvider.GetDefaultFolder()
   at Microsoft.Exchange.Data.Storage.Management.EwsStoreDataProvider.<>c__DisplayClass1b`1.<InternalFindPaged>b__13()
   at Microsoft.Exchange.Data.Storage.Management.EwsStoreDataProvider.InvokeServiceCall[T](Func`1 callback)
   at Microsoft.Exchange.Data.Storage.Management.EwsStoreDataProvider.<InternalFindPaged>d__21`1.MoveNext()
   at Microsoft.Exchange.Data.Storage.Management.AsyncOperationNotificationDataProvider.<GetNotificationDetails>d__57.MoveNext()
   at System.Linq.Enumerable.WhereEnumerableIterator`1.MoveNext()
   at Microsoft.Exchange.Servicelets.CertificateNotificationServicelet.RemoveAllNotification()
   at Microsoft.Exchange.Servicelets.CertificateNotificationServicelet.UpdateDataInMbx(List`1 certificates)
   at Microsoft.Exchange.Servicelets.CertificateNotificationServicelet.Work()