Last evening, I tabbed to Windows Live Mail to check email (usually leave Live Mail open) and EVERY single email in EVERY folder spontaneously duplicated as new, unread emails in the Inbox over the following 45-60 seconds.  I immediately closed any open applications/windows and re-ran Security Essentials and Malwarebytes full scans (both apps were up-to-date and are scheduled to run daily).  Nothing found.  I've observed no other unusual activity since then.  I have only ONE email account associated with Live Mail through our ISP, Atlantic Broadband.  I checked with the ISP and they cannot offer an explanation.  Can you suggest what might have caused that activity?