Hi,
You said ICS to share internet. Well i have something similar when sharint the internet on a XP box using ICS and other two PC's with ME. I check KB from M$ and found nothing.
Finally i gave up and setup the DSL connection on a Dlink Gateway, and all the HW on it. It started to work fine.
Maybe is the ICS thing, i tryied several times with no luck.
Just a Thought!!

Kitain