This error is often fixed by just restarting the computer. However, shouldn't a restart fix it, it is recommended to uninstall and reinstall your Norton product, using the Norton Removal and Reinstall tool which will get you a fresh installation. Here is the link: www.norton.com/nrnr
Before running it, please read the "Before you begin" section.
After running NRnR, run LiveUpdate manually a few times, rebooting as requested, until no updates are available. When finished I'd reboot anyway,even if not prompted, it never hurts...
Let us know how things go.