Norton programs, no matter what they were have always caused problems on every system I've ever seen them installed on. I won't touch Norton Products.
I use InoculateIT at work. Still running on version 6.0 but its awesome. Auto updates so I don't have to babysit the antivirus signature site. I can scan my network to see which PC's are on and off, what signature version they're running, what OS they are, etc. Can also define "Organizational Units" with pre-defined "profiles". For example if I install it on a server, I can drop that server into my "Signature Servers" OU and suddenly its avaialble for signature downloads to other PC's. Alternately, if its a end user I can drop them into the "unable to modify their own settings" OU so they can't disable their antivirus. In about 2 years of running InoculateIT only 2 "viruses" have attacked my company. And they weren't really "viruses". The first one was one of those emails that provides a link to a site on the web and the user was a corporate boss so he had admin rights to install what he didn't know was spyware. Would have been prevented if he didn't have admin rights. The 2nd was that ms blaster worm, which was because some users weren't up to date on their service packs. Overall it's performed great. Of course, this is from a corporate review standpoint. I understand they make something for end users, it might be worth checking out.