If you are having problems with onboard LAN card, you can try a BIOS recovery as this could be a problem with your motherboard BIOS,
If you want to perform BIOS recovery, check instructions here:
Additionally, I remind you that your board is no longer supported by Intel technical department.
Not sure which package you downloaded for your drivers. Maybe the driver package you tried did not include the driver for your board. After you try the BIOS suggestions, you should try downloading the older version of PROXP.exe listed for your desktop board.
Sorry for the delay, I only had time over the weekend to try out that.
I tried Express BIOS update, but that too did not make any difference. Since I already had the latest BIOS update applied (before the crash) could it be that updating it again is a noop? I have also tried using various hardware detection tools and they can't find out any network interface. For example, used partmagic's utility.
The LED on the back of the chassis is lit green when it's wired, so that makes me think it might still be alive.