When my laptop connects to the internet, it does so via my wireless network. I have a cable modem plugged into a server machine on which one virus checker (Norton), and Zone alarm sit. This then goes out in infrastructure mode (encrypted), to a number of laptops including the one I am having trouble with which is running AVG as a second layer of protection. As such, there is no interference between the two virus checkers. I never dial this machine into the internet and in fact, there are no dial up connections configured at all.
I have paired the startup on this machine down to the absolute minimum, even running it safe mode and still occasionally the lock up occurs. One other charateristic when it fails is the hard disk light being on permenantly. As it is more flakey on battery, I have a suspision that power comes into it somewhere