|From the sounds of the problem and the troubleshooting steps you've already taken, I suspect your NIC has failed and is in need of replacement.|
I would definitely try another NIC.
If a new NIC also doesn't work, you will likely find your only resolution is to do a clean install of your operating system.
You could (and should) first try uninstalling and then reinstalling the TCP/IP stack but if that doesn't work, the only recourse left to you would be the clean install.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.