Hi. Got an automated response from a 'bot at Stardock.... with a random selection of unrelated tutorials.
For what its worth I have tested by (a) disabling Norton 360 and ( added a specific firewall exclusion between the 2 PC's - all ports, all traffic - no change.
ARP reports the mac addresses from both machines (and they match!)
Ping both ways - no probs.
RDP works just fine.
etc etc etc.