My problem is only with sending emails, not picking up pop email, so I wonder if you may have a different problem. If you have windows xp, then go start >> programs >> accessories >> system tools >> system restore, then choose "restore my computer to a previous time" and on the next page simply pick a date which is highlighted before you applied the update. You'll then be asked if you're sure and it will reboot and do it's business.
If you've got windows ME, then I think it's the same... although if you've got ME, I've seen plenty of problems with that and NAV this year, so you are better off either using a different AV package or burning your computer and buying a new one with XP.
I'm also waiting on a reply from Symantec tech support - they are currently telling me to try all the things I've already tried....