When you use wireless, it would most likely be the 192.x.x.x range, if you then enable internet sharing, I believe that it tries to set your local pc to 192.168.0.1 and act as the network router which would mean that you get routing problems.
If I was you, write down the ip that you get from the wireless network, if it starts with 10, go to step a, if it starts with 192, go to step b.
Enable internet sharing through the normal method.
Go to control panel > Network and Internet > Network Connections (I am using Win 7, but I think it is the same).
Right click on the wired network card and click properties, then double click TCP/IP Settings
Set your machines IP to 192.168.0.1,
Set your machines IP to 10.0.0.1
Set Subnet Mask to 255.255.255.0
Set Gateway to the router's IP address
Set DNS either to openDNS or the IP of the router (depends on features you use)
Now, on your other pcs, you may get incorrect DHCP leases. Set it to manual as above but use.
IP 192.168.0.x (must be unique)
DNS either opendns or 192.168.0.1
IP 10.0.0.x (must be unique)
DNS either opendns or 10.0.0.1