Updated subscription 2 days ago. Before that everything has been running fine for years. Now since the new subscription full scan and quick scan hang when they get to the point of scanning common areas, always on the scan for W32.Downadup.b. It's never done this before. I have removed and reinstalled Norton 360 and it still does it. I have read through the forums and tried the things suggested in some of the posts to no avail. Would anyone else have any suggestions how to restore it back to normal working conditions? When I click on stop it just switches to Pausing...
Thanks for the reply's all.
Did a quick scan last night (maybe not so quick), it did actually complete... but took 14 hours! 
I'll see how it goes over the next few weeks.
Hello Kas64. Reboot your computer, disconnect from internet services and run a fresh quick scan. If it completes that could be an issue that your network is somehow compromised.
SA
Thanks for reply's. System is clean according to Malwarebytes. It does not state which file its checking when it hangs, just "Checking for: W32.Downadup.b"
The scan normally used to take around 5 mins... have waited over 12 hours for it to finish (left over night).
Have also run LiveUpdate several times as well.
Previously disabled Fast Startup as knew this had issues before hand. CPU usage is around 50 % when I start the run, but drops to 10-15% once it hangs.
FYI The malware that is shown in the scan is what Norton is scanning for. Not what it is detecting on your system.
How long are you waiting for the scan to complete?
Be sure you have run LiveUpdate manually a few times, restarting as necessary, until no updates are available. Restart, not shutdown and startup again if you have Windows Fast Startup feature enabled. If you use Windows 8/8.1 or 10, there can be an issue with the Windows Fast Startup feature.. See more information here.
It is likely malware and you need to remove it. Try running Malwarebytes free scanner to see if it detects it.
Also, Google the file name and you will find various methods to remove.
https://support.norton.com/sp/en/us/home/current/solutions/v59829348
https://www.softpedia.com/get/Antivirus/W32-Downadup-Removal-Tool.shtml