I, for one, can’t see any way that PXE or FOG could cause this situation.
Was the NIC actually working in the 2K box prior to capturing the image? Not knowing how it is used, I could imagine a situation where the NIC had been down for some time, you image it, someone notices the NIC isn’t working, and since you touched it, you own it (in their mind), even though there isn’t a way FOG or PXE couldn’t have changed things.
I might check the network cable, especially if a different cable was used for capturing the image. Or the pins on the NIC, wall jack, hub/switch/whatever else it’s connected to. I’ve seen pins pop out, get crossed, and other strangeness.
You could also try a safe-mode boot and see if that gets you anywhere as far as being able to log on. Or even an Ubuntu LiveCD. If you’re getting network connectivity there with the same cables, etc., I’d guess it is a driver issue.
Only other possibility I can think of (and this is pure speculation) is there might be a damaged bit of the hard disk where the NIC driver (or other files) live and aren’t able to be read. Perhaps the activity on the disk pushed it over the edge, but it would have failed sometime soon anyway in that case. Short of being able to log onto the 2K installation, I don’t see how you’d be able to troubleshoot this one.
You’ve demonstrated the NIC still functions, FOG doesn’t change anything on your computer when capturing an image (as I understand it), and you had no way of logging onto the computer to change anything.