NIS 2012 Identity Safe Log-ins disappear on two computers

My laptop and desktop, both running Vista and IE9, lost all of their Identity Safe entries yesterday.  Fortunately, this issue had a happy ending, as I had recently uploaded them to Norton's server in order to stay synchronized.  That enabled me to easily download the log-in data to restore the large number on both machines.

 

Anyone have any ideas on what could have caused this problem with NIS 2012... perhaps a glitch in a Norton update, or the latest IE9 fix?