Suddenly Outlook starts prompting password

Hi,

I am experiencing Password prompt issue with Exchange 2013 CU2. It happens twice, Outlook starts prompting password or show disconnect and do not accept the password. After some time problem automatically disappears. I am not able to find why it is happening.

Below is one event i have noticed in the App...

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Log Name:      Application
Source:        MSExchange Certificate Notification
Date:          18-09-2013 15:19:21
Event ID:      2001
Task Category: General
Level:         Error
Keywords:      Classic
User:          N/A
Computer:      B--------h-Cas02.b-------h.com
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()
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="MSExchange Certificate Notification" />
    <EventID Qualifiers="49152">2001</EventID>
    <Level>2</Level>
    <Task>1</Task>
    <Keywords>0x80000000000000</Keywords>
    <TimeCreated SystemTime="2013-09-18T09:49:21.000000000Z" />
    <EventRecordID>32776</EventRecordID>
    <Channel>Application</Channel>
    <Computer>Bestech-Cas02.bestech.com</Computer>
    <Security />
  </System>
  <EventData>
    <Data>Microsoft.Exchange.Data.DataSourceOperationException: The request failed. The remote server returned an error: (401) Unauthorized. ---&gt; Microsoft.Exchange.WebServices.Data.ServiceRequestException: The request failed. The remote server returned an error: (401) Unauthorized. ---&gt; 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&amp; 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.&lt;&gt;c__DisplayClass1b`1.&lt;InternalFindPaged&gt;b__13()
   at Microsoft.Exchange.Data.Storage.Management.EwsStoreDataProvider.InvokeServiceCall[T](Func`1 callback)
   at Microsoft.Exchange.Data.Storage.Management.EwsStoreDataProvider.&lt;InternalFindPaged&gt;d__21`1.MoveNext()
   at Microsoft.Exchange.Data.Storage.Management.AsyncOperationNotificationDataProvider.&lt;GetNotificationDetails&gt;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()</Data>
  </EventData>
</Event>

Best Regards, Ranjit Singh