To be honest the best thing you can do is to uninstall the Norton software from your system. There are no (as in none, zip, nada, zero) viruses for OS X so it's using valuable system resources and will eventually cause more problems than it solves. These forums are full of users that have antivirus software installed on their Macs that have nothing but trouble. Yesterday I helped another user that was experiencing Kernel Panics caused by their antivirus software. Once it was removed the system returned to normal. Follow Norton's instructions for uninstalling their app.
The ONLY reason for any antivirus software on a Mac is if you are in the habit of download files from unknown sources and then passing those files on to MS Windows users. While OS X is immune the Windows users are not. If you feel you must have antivirus software then I'd recommend ClamXav which is much less intrusive and kept up-to-date.