I rely heavily on Norton Internet Security's automatic fill in because, living in China, I do everything online. But when I upgrade to 2012 from 2011, the Identity Safe automatic fill in quit working. I searched the internet, read numerous official and unofficial solutions--including the one about updating Norton internet security several times, rebooting each time. Nothing worked.
But it works now and the solution came to me courtesy of a Firefox reminder. Somehow, I had disabled the Norton Add-on and toolbar on Firefox. I enabled it, closed and reopened Firefox, and it works like a charm. So if you face this problem too--try the toolbar and add-ons.