It seems the Network prefs window is one of few settings windows where you have to Apply your changes before they take effect. I clicked on Apply and now it works.
"None of these answers fixed my problem, but this worked for me:
Copy /System/Library/Extensions/AppleUSBEthernetHost.kext to a backup folder (Desktop) and delete the original Re-download the latest version of iTunes (http://www.apple.com/itunes/download/) Install iTunes, this will update your ""AppleUSBEthernetHost.kext"" file. Disconnect USB-connection to iPhone Re-connect iPhone via USB"
