Ethernet connection problem - help!

We have a computer (some off brand, FTC) that we just got a new Ethernet card for. We put the new Ethernet card in......everything goes fine, then when we try to make the network connection, we get the error message that something is not connected. The Device Manager tells us that the hardware is working properly. The cable we're using definitely works, because we can network 2 of our other computers without any problems. We cleaned the slot on the motherboard, and even un-installed and tried a different slot. We can't even finish the "Network Set-Up Wizard," beceause it says something is "not connected." The drivers are all up to date and apparently installed properly. Any ideas how we can get this to work?