Well, the likelihood that you zapped both DIMMs in the same address range is pretty darn low. I would say that something failed on the board or in the processor. Time to directly contact Intel Customer Support and talk to them about an RMA. Start here: Contact Support.
OK, I got to chat with 'Warner', gave him my info and a link to this thread.
Gave him the NUC S/N, etc. and arranged for a warranty replacement.
Got contacted by phone, arranged for an overnight swap.
So far, so good. Will post again after I get the new unit running.