...the VCP drivers from FTDI (CDM 2.08.24 WHQL Certified) are nice and signed. They install successfully, and Device manager shows a new entry "ATmega16U2" under a new class "Atmel USB Devices". No yellow exclamation mark, and its properties look good.
I am using an arduino ethernet, not a mega. I know there are many versions of arduinos out there. However, the ethernet is basically the uno R3 with a built in etherenet shield.