Antivirus Warning -- is my computer briefly at risk when I boot it up?

[teddyFBI]

I have a good Symantec antivirus program through my grad school...but I've been noticing that when I boot up my laptop, I immediately get a Symantec warning popup in the lower right that tells me that Symantec Antivirus is off, and that my computer might be at risk.

Then, however, the antivirus program goes ahead and activates as part of the normal sequence of booting-up activities, and when all is settled, it's running and protecting my computer just fine.

What I'm wondering about, though, is if my computer is at risk for those few seconds when my ethernet cable is connected (and hence I'm guessing I'm technically online), but before Symantec has actually initialized and begun running. When I first bought my laptop, I learned that hard way that many worms/viruses (MSblast for me) can basically attack you within literally seconds of the moment you get online unprotected. So I was wondering whether I am at all at risk during those few seconds when Symantec has apparently not started up yet...