Well I think some of you are being a bit unfair to Norton here!
I've used their AV with ZoneAlarm Pro on four computers now and it has all worked well and in harmony.
The people I have come across that have had Norton problems have often caused them for themselves, albeit unwittingly, by mixing their security programmes, using two AV programmes, or Norton Security plus other pop-up and Adware programmes etc. instead of leaving one programme alone to do what it does best.
Of course it helps if they are properly installed and configured in the first place but, like many others, I get bored reading the instructions!
Just my 2d.