confirmed that this is still an issue with the most recent BIOS, i reproduced it today. using this motherboard in a NAS box. both SATA ports filled + 4 more in a promise PCI card, USB keyboard, booted from a USB memory stick into a FreeBSD install several times, could format drives and install the OS fine, but never got a NIC detection.
pciconf showed nothing resembling a network card.
pulled the power plug for 20 seconds and fired the machine back up without the USB key attached, and the previously installed OS then picked up the NIC just fine, and it stays after reboot.
i upgraded to the most recent BIOS before running across this post, that made no difference, the problem persisted until the power was pulled.
I, too, just experienced this problem. I run Slackware Linux 13.1 on my D510MO machine and, out of the blue, no network access. ifconfig, lspci and dmesg revealed that it wasn't seeing the NIC. After trying power-cycling, my reaction was that the board had failed, but fortunately, I found this thread and pulled the plug, which restored order. This problem needs to be reported to Intel (assuming discussing it in this group isn't sufficient) if it hasn't already. I'll look into it.
Thanks again for providing the workaround that got my machine up and talking to the network again.