FYI, I've had the same issue on two different machines, in both cases in trying to install CoS7 in a VM. I've tried using a legacy virtual NIC, no dice. Both have different Realtek chipsets in the NICs (onboard, in both cases) - one's a 4-year-old Dell and the other's a 2-year-old Gigabyte MB with AMD chip/chipset. Hard to avoid the problem - I'd hazard a guess that 75% of the boards I've used in the last four years have Realtek chips on them.