i got that one yesterday too. It is the first one that I have got since I started not opening attachments off of e-mails. I have no idea how I got this one.
Annoying as hell. Does not shut your computer down when you are not connected to the net, and when you get the shut down error message, if you set your calendar back a couploe of days it resets the time remaining to a couple of days and not one minute. That way you can down;oad the fix etc without the computer shutting down. Go to www.norton.com
on the main page is the info on this virus, as well as the fix and the security update for windows.
Hope that helps others infected.