Well... silent mode does nothing in regards to the "needs attention" status. For that matter, silent mode doesn't seem to do anything at all that my settings don't already deal with--except extending the 20-minute delay a bit (but as mentioned, if I leave the laptop alone for that long, it's usually hibernating anyway). The nuisance of turning silent mode on ("really? are you sure you want to enable silent mode? you won't change your mind? ok, then, for how long?") really limits its value, as well. (Why can't there be a single-click on/off? I mean, come on, turning it on and then forgetting it isn't like, say, leaving the stove on, or leaving the car running in the garage--nothing bad will happen if you forget to turn silent mode back off again. So why is Norton so *bleeping* paranoid about it?)
So... screw silent mode. However, despite all the stupid things it does, XP was actually quite helpful in resolving my issue: if you ignore the Norton "needs attention" exclamation mark for long enough, the icon becomes "inactive", and Windows hides it for you. This is kind of special, as I have the normal (green checkmark) Norton icon set to "always show"; thanks to the same idiotic simple-mindedness that refuses to keep the wireless network icon hidden (each variation of wireless networks available seems to register as a different icon condition, in regards to the "hide inactive" function), if you have Norton (green checkmark) set to "always show", it still reverts to "hide when inactive" when it goes yellow exclamation on you.
So, the moral of the story is: if you ignore the Norton "needs attention" status for long enough, it will go away (at least, in XP's task bar thingy--I don't know if it works for Vista/7 or Windows Tablet (ie., 8), and honestly, I couldn't care less). Three cheers for apathy, and whatnot: problem ignored = problem solved.