This issue has never resolved:
It's been two months since I wrote this post and the problem has never been resolved, either by Norton Chat as well as with Norton Community.
As I already explained the issue appears only with Windows 8.
During these 2 months, I have formatted the hard disk of the PC and installed Windows 7 sp1. I've installed the same software and have configured the OS same as when I had Windows 8 Pro.
Besides my account with administrator privileges, I created 2 additional Standard Accounts.
NIS 20.3 worked properly and I always had 2 "Symantec Framework" running as it should always be.
Four days ago I reinstalled Windows 8 on the same PC, same configuration, and the problem reappeared when I updated to NIS v.20.3
On the Task Manager reappeared "3 Symantec Framework" running, and today there are 6!!!
To temporarily resolve the issue problem I've to do a reboot, but the problem returns after a couple of times that I turn off the PC.
I want to reiterate that NIS has never given these problems up to version 20.2.
It 'obvious that the problem is caused by NIS 20.3 (both 20.3.0.36, and 20.3.1.22) that don't work correctly on Windows 8 (multi account).
This is a BUG that is present on NIS 20.3 !
I hope someone of Symantec read this message and solve the issue.
I can't and don't want to change the OS for running NIS correctly. Hopefully I should do the opposite, change NIS with another security software.
I'm a fan of Symantec and I would not be disappointed.
Thank you!
Sandro