If you need help to get rid from Norton, just let me know… 
Yes, maybe a clean install could help (unless you had desinstalled Norton from your computer a few time ago… and do not have reformated your HDD after… 8))
Why don’t you follow another way:
- Download avast! 4.1.289
- Desinstall your actual version of avast (Control Panel).
- Boot
- Use Avast Uninstall for complete desinstallation.
- Boot
- Install the downloaded 4.1.289 and see what happened.