The wireless lan was using DHCP. Since you no longer use it, the computers have no way of optaining an IP address so you have to set them manually

Set one machines IP address to 192.168.0.1 and the other to 192.168.0.2. Both should have a Subnet mask of 255.255.255.0 and set the workgroup name to anything you want just as long as both machines match. .