First thing I'd try is plug the ethernet cable into your Mac again, launch SysPrefs > Network, and see if Ethernet reports that it is connected.

(I have no idea if this makes any difference, but have you tried turning airport off when you've got the ethernet cable plugged in?)

The new Great Equalizer is the SEND button.

In Memory of Harv: Those who can make you believe absurdities can make you commit atrocities. ~Voltaire