Hi Anil,
Thank you so much for your instructions.
My problem was the same as StefanB's. It started after I updated Windows 8.1 on 08-12-2014.
Today (8-30-2014) I found your instructions. So I went to Lenovo download site, and I got Realtek Driver
(v 8.2.612.2012). Then I shut down my computer, and I waited for 60 seconds before starting my computer again. It worked. My HYPER V computer can join the network.
I built my computer myself using following parts last DEC 2013.
Motherboard: MSI H81M E33v2
CPU: Intel Pentium G3220
OS: Windows 8.1 Pro (64) Update 2