I remember having this same issue on my old powerbook. However, I don't remember how to fix it, and I haven't found the solution after fooling around with my system preferences. Basically, when I leave my computer idle for a certain period of time, my internet connection disconnects. (My iChat logs out, etc.) When I get back, the internet reconnects again after a few seconds. I'm on a college ethernet connection. Anyone know off the top of their head where I can disable this auto-disconnect with idle feature?