...if you've installed iPhone Configuration Utility....
....you need to do a "sudo kextload /System/Library/Extensions/AppleUSBEthernetHost.kext" in Terminal and it's working again.
I don't know if it stops iCU (iPhone Config Util) from working, but if it does: "sudo kextunload ..." (still in Terminal!)
iPhone 4, Mac OS X (10.7.4), iPhone Configuration Utility