Does yours have any lighs on either side of the jack that flash when in use?
Mine does not- and I have had issues getting ethernet to work when going from wireless to ethernet, or coming out of different modes (sleep, etc.) The controller has the drivers installed and shows as functional in Device manager with no flags.
But step 1 is to see if the jack is faulty, as I see no network activity LEDs in there- but maybe this jack doesnt have them. I do get it to work eventually (dont know how), and I am on ethernet now.
WIndows 7 troubleshooter says bad cable- but I tried 2 cables that are currently in use with 2 other machines, so I know theyre good (onre cat 5, one cat 5e.)