Your link says:
Do not use ICS on a network with domain controllers, DNS servers, gateways, or DHCP servers. And don't use ICS on systems configured for static IP addresses.
You need to prevent the Mac getting an IP-address from the wifi router (which probably acts as a DHCP server).
I would try
- disable DHCP service on the router
- set a static IP address on the PC (I assume the last sentence above applies to ICS clients)
- set the Mac to use dynamic addressing
Hopefully the Mac will then pick up an address, and routing details, from ICS on the PC.
Update: A MacWorld Article says
On the client computer (Mac OS X and a wireless NIC):
- Click on the AirPort icon at the top right of the screen.
- Click Create Network. A dialog called Computer-to-Computer should pop-up.
- Set name to ICS. Click OK.
- Open System Preferences from the Apple menu.
- Click the Network icon.
- Select AirPort from the Show Menu dropdown.
- Click the TCP/IP tab.
- Select Manually from the Configure IPv4 dropdown.
- Set IP Address to 192.168.0.2.
- Set Subnet Mask to 255.255.255.0.
- Set Router to 192.168.0.1.
- Set DNS Servers to 192.168.0.1.
- Click Apply Now.
You have now completed setting up the client computer. Read on for the host computer instructions.
On the host computer (Windows XP, Internet Connection (i.e. Cable or ADSL), Wireless NIC):
- Click Start -> Control Panel.
- Double-click Network Connections.
- Right-click Wireless Network Connection and then click Properties.
- In the General tab, select Internet Protocol (TCP/IP).
- Click Properties.
- In the General tab, select Use the following IP address.
- Set IP address to 192.168.0.1.
- Set Subnet mask to 255.255.255.0.
- Click OK.
- Click the Wireless Networks tab.
- Click the View Wireless Networks button.
- Select the network named ICS from the list and click Connect.
- Click OK at the next dialog telling you the network is open.
- Close the View Wireless Networks window.
- Click OK to close the Wireless Network Connection window.
- You should now be in the Network Connections window.
- Right-click Local Area Connection and then click Properties.
- Click the Advanced tab.
- Click the Allow other network users to connect through this computer's Internet connection checkbox.
- Click OK.
You have now completed setting up your Host. You should be able to connect to the Internet on your Mac. If you follow these instructions, your wireless connection between your Mac and PC will be unsecured; it is highly recommended you set a WEP password.