The 2008 edition of Norton Internet Security is definately one of the greatest commercial security softwares available today.
It's newbie friendly, Lots of protection, It doesn't suck your memory resource like previous editions AND you can use the same copy on 3 different systems.
Now for the error.
More and more pople experience that their auto-protect feature is disabled on default.
If you turn it back on it will turn itself off again a short while later.
Now it doesn't really matter if you re-install or not cause the error will return with time.