I was running a Nitro board with a G3 upgrade using mc without much of 
a fuss. Are you absolutely positively without a doubt certain that: 
your cable is wired correctly, autonegotiate is enabled on the switch, 
and all pins are making contact What happens if you change the ifmedia 
to 10BaseT-Half duplex (even though this is probably what ifconfig 
reports already).

I'd test 2.0 but I no longer have the machine.