Well, you see, the 'board was connected to a USB to Serial bridge which in turn was plugged in to the laptop. As soon as I touched the other 'board power line with the second lead, Luna shut off. [2/4]

Thing is, I had plugged the charger moments before to measure its output (about 15v, actually) then disconnected it afterwards. I just forgot that the thing kept its power even after unplugged and that stored charge ran through Luna's USB port... [3/4]