An error occurred while Internet Connection Sharing was being enabled. (null)?

[johntrottier]

What is it that you are trying to do?

ICS is Microsoft's way of letting you share an Internet connection without a router.
Usually you have:
Internet from a modem using a USB or wireless connection and a second computer connected to the Ethernet network adapter.
Do you actually have a second computer connected? is it set to obtain it's IP address automatically.
The error message sounds like the second computer is not being detected.
Hope this helps