Hi,
Maybe someone else will offer you another option, but the two I can think of are;
- Try uninstalling / reinstalling www.norton.com/nu16
- Contact Customer Support - they may want to remotely access you machine to diagnose. www.norton.com/chat
Have you installed Vista Service Pack 2?
Have you run Smart Update in NU?
Sorry, but that's the best I've got. I hope it helps.