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Posts: 5
Registered: ‎07-13-2011

Error 8506, 421



The error in the subject line keeps appearing. What I already tried was re-installing which didn't help.

Then I got live-support by chat and it helped for about 2 days.

Then I got live-support by telephone and they upgraded from AV2012 to AV2013 and again it helped for a few days

and then it came back again...


Anyone know a solution?


Thanks in advance for your reactions.


Greetings from Belgium!

Regular Visitor
Posts: 8
Registered: ‎09-11-2012

Re: Error 8506, 421

Hi Eyes-T,


Try to run the Norton Remove and Reinstall tool.


restart the computer and check if the issue has been resolved.

Posts: 10,059
Kudos: 2,249
Solutions: 512
Registered: ‎12-02-2009

Re: Error 8506, 421

Please ensure you have no other security porgrams installed either presently or had them installed in the past that could may not have been removed totally (as by running their removal tools after removing via Control Panel).


Please double check that Windows Defender is disabled - it is one of the security programs that run in real-time and can cause a conflict with Norton.


Also please verfiy that 8506, 421 is the correct error number.

Posts: 1
Registered: ‎09-25-2012

Re: Error 8506, 421

Nothing help I use The Norton Removal Tool ,Norton AntiVirus 10 time and don't work ,One message is ,Norton 360 reports it is turned off, I tray turn it on and say Norton 360 has not provided windows with a program to fix this issue . This happened after update My windows is 7 ,home premium plz Help

Regular Contributor
Posts: 45
Registered: ‎06-22-2012

Re: Error 8506, 421




Manually remove Norton using NRT and after that delete the entry HLKM\System\CurrentControlSet\Enum\Root from registry. Before you do that, make sure you have backed up the reg data. And after that reinstall the Norton program.

If this did not help, please restore the system to an earlier point of time and try installing Norton. If the windows installation is new and you are still getting the same error, format the "C" partition, perform a clean installation of Windows.


Hope this helps.




Regular Visitor
Posts: 6
Registered: ‎08-15-2012

Re: Error 8506, 421

Wouldn't it be easier to use another anti-virus than do a system reload. That's what I did.

Regular Visitor
Posts: 5
Registered: ‎07-30-2012

Re: Error 8506, 421



Try these steps. It looks a bit complicated but it does work.


1. Go to Control Panel and uninstall NAV/NIS (choose delete all files option) then restart 


2. Download and Run Norton Removal Tool then restart again


3. Open Device Manager. Click "VIEW" then select "Show Hidden Devices"


4. Expand "Non-Plug and Play Drivers"


5. Uninstall NAVENG, NAVEX15, Norton Antivirus Settings Manager, Symantec Data Store to SymEvent (this includes all entries starting with Sym)  Select "NO" when prompted to restart


6. Open Program Files folder, if you find Norton and Symantec Folder delete it


7. Delete temporary files (open "run" then type %temp%)


8. Restart system then download and re-install Norton


9. Run Live Update


Hope this helps.