Yeah, as I said, I don't think that's an easy device to open. Me, I'd open it because I'm a bit cavalier about a few nicks or dings. I've actually destroyed a brand-new device once before I even used it in the slightest! Oh, well, such is the price of a little bit of fun.
Did you try reinstalling drivers for the fastboot? Is it showing warnings in the Device Manager? Does anything work?
Code:
C:\>fastboot getvar all
Normally ??????? is a pretty big failure, meaning that it couldn't get the serial number off the device. This could be as simple as a bad USB cable. It could be that the interface was never correctly initialized.
Download this utility. Run it. Plug in your Leaf and/or unplug it and see what appears/disappears. Select the Leaf in the left hand panel, look at the right hand panel, it had better be longer than two short paragraphs.
https://www.ftdichip.com/Support/Uti...crosoftUSBView
You can also run my utility at the same time. It's unrelated and won't interfere with anything.
http://www.temblast.com/windows.htm -> usblog.exe
It tells you when things are connected/disconnected. If you get Windows "bongs" but the list in UsbLog doesn't change then you're probably missing a driver or hardware problem.
Did you have ADB working on the regular boot previously?