Mine is a fresh install as of monday as well...
from some digging, looks like some people on 2k8 Server are having this issue as well...
What NICs do you have installed? I'm running a TP-Link TL-WN851N, and Dual onboard gigabit (who's controler escapes me right now)
i think i'm going to try reinstalling all the
drivers from their manufacuters instead of using whatever windows decided would work.