Earlier this week, Symantec published technical details of a security flaw that affects many of its consumer and enterprise products. (Read Symantec UPX Parsing Engine Heap Overflow for the gory details.)
If you use Norton AntiVirus 2003 or 2005, you’re OK. If you use Norton AntiVirus 2004 or Norton Internet Security 2004, you might need to download an update manually. I don’t have Norton installed here, but if I recall correctly the default settings for Symantec’s Live Update only deliver updates to virus definitions. You may need to run LiveUpdate manually to get the updated program code.
If there are any current Norton users out there who can fill in other details, please leave a comment.
Ed Bott 
Yes, Norton Anti-Virus is not capable of self-updating itself with bug fixes. This is true for all versions of NAV.
Reading the manual for NAV 2004 is an interesting lesson in doublespeak as they try to say this without saying it. For the details on this see the NAV 2004 gripes on computergripes.com.
NAV has an option to tell the user that bug fixes need to be applied, but it may not always work and may be mis-understood. Then again, why should this be an option at all? I’ve seen an XP machine where NAV stopped running at boot time after applying some Windows bug fixes. Live update was running fine, NAV was up to date on virus definitions. Manually running Live Update and applying the outstanding bug fixes to NAV fixed the problem.