I doubt anti-virus, firewall or malware protection is the issue. I disabled all on the Win8 machine and it made no difference. Other reasoning is that I use the same malware app on both the Win8 and Win7 machines, yet different virus protection. Since the hang started immediately after upgrading to V16 from V15, while not changing any other settings on that machine, it's reasonable to assume that there is something going on in V16 itself. Reproing the issue with a brand new machine and a clean install of V16 also leads to it being a bug in V16.
I did export the sites from V16 on Win7 to a csv file and imported them to the Win8 machine.