Ethernet port doesn't work anymore
Have you tried to reset your network settings to default?


Turn off your WiFi and unplug all network connections
Go to /Library/Preferences/SystemConfiguration
Take a backup of the preferences.plist by renaming the file to preferences.plist.bak (just in case)
Reboot and a new preferences-file will be automatically recreated


... and by so your network settings will be restored to the default.
Don't worry, it's all about settings, not stored data (like names of networks) will be erased.