I just had the symefa.sys BSOD.
Running a fully updated Internet Security 2012 with default settings.
Newly installed and fully updated Vista SP2 32-bit on a Sony Vaio. RAM and DISK tested ok.
While the BSOD happened I was copying files from a USB drive and had just started Windows Live mail.
There are many old threads about this for 2011 and older versions but they cannot be replied to so I started this one.
I have a 450MB kernel dump that I'd be happy to send to any Symantec staff.