iPhone USB Tethering stop working after iOS 5.1 update

USB Tethering stop working (while WiFi and Bluetooth tethering continue to be ok) on Mac 10.6.8 (Snow Leopard fully updated) after my iPhone device has been updated from iOS 5.0.1 to 5.1.

The present issue is not related to the iPhone (Personal Hotspot ok, Carrier/APN settings ok).

Moreover, USB layer seems to be ok on Mac also due to the fact that iTunes recognizes it correctly.

Network Services on Mac are instead affected.

Steps to Reproduce:

1. Remove 'iPhone device' from Network Preferences;

2. Connect iPhone via USB cable to the Mac;

3. A new 'iPhone device' does not appears while the /var/log/kernel.log says:

[DGMTP_Drv.cpp][probe()][00103][ERRO] Current vid (0x05ac) and expected vid (0x04e8) is not matched

Other interesting information preceding the mentioned above error on kernel.log are:

kxld[com.apple.driver.AppleUSBEthernetHost]: The super class vtable '__ZTV20IOEthernetController' for vtable '__ZTV20AppleUSBEthernetHost' is out of date. Make sure your kext has been built against the correct headers.

Mar 13 15:08:25 carlo kernel[0]: Can't load kext com.apple.driver.AppleUSBEthernetHost - link failed.

Mar 13 15:08:25 carlo kernel[0]: Failed to load executable for kext com.apple.driver.AppleUSBEthernetHost.

Mar 13 15:08:25 carlo kernel[0]: Kext com.apple.driver.AppleUSBEthernetHost failed to load (0xdc008016).

Mar 13 15:08:25 carlo kernel[0]: Failed to load kext com.apple.driver.AppleUSBEthernetHost (error 0xdc008016).

Any Suggestions?

Thank you.