Windows won’t let me work online on my e-mail.

  When trying to get into my e-mail account I can't work online.  The following message appears : 'There was an error when attempting to connect to the Windows Live Calendar service. If the error persists, check to see if there's an upgrade of Windows Live Mail available or contact a service representative.' I have had this problem before and managed to fix it with your help and others.  However I can't remember how!  SO frustrating!