Like you noted, Norton AV is very good, with that one exception. Fortunately it is easy to turn that off.
I, like you, have been using Norton for years, and prefer it to McAfee (which I have tried). You're not going to get a perfect anti-virus program as the virus programmers are always looking for, and sometimes finding, ways to get around the anti-virus protection.
The only way to make your system 100% uninfected, would be to not connect to the internet and not install any software at all, including an operating system.
