My Macbook can connect to ethernet over Ubuntu but not OS X
If you can see the interface in /Utilities/System Configration > "Ethernet Cards", try creating a new network location.

If the issue persists in a new location, you can reset OS X's detected network interfaces by (re)moving /Library/Preferences/SystemConfiguration/NetworkInterfaces.plist.  If you want to play it absolutely safe, you could (re)move the entire SystemConfiguration folder, but this will affect other settings (like custom network authentication, power management settings, etc.). NOTE: this step supersedes testing it in a new user since it removes global preferences (which affect every user).

If you're still not seeing it, try booting to your Recovery Partition, launching Terminal, and running ifconfig to see if the Recovery partition can see the network interface.  If the Recovery Partition sees it, a reinstall of OS X might be needed.  If it doesn't, well then you did something that I've never seen... :)