Symantec is aware of this issue and is currently investigating it. This document will be updated as soon as more information becomes available..
http://service1.symantec.com/support/ent-security.nsf/docid/2010061410233448?Open&seg=ent
( THIS IS A WORK AROUND)
Take the backup of the regisrty and then
Navigate to HKEY_CURRENT_USER\Control Panel\Desktop\ AutoEndTasks and set the value to 1
https://www-secure.symantec.com/connect/forums/ccapp-preventing-computer-shutdown-and-similar-issues