I have discovered some even more interesting behavior, and have gathered the requested log...
I noticed that Internet access didn't seem to be affected the way Windows Networking is, so after starting a folder copy operation, which was seen to immediately stall, after a few minutes I decided to run a speed test to a test site on the web.
Lo and behold, while the speed test was in progress the stalling, failing folder copy between Windows systems immediately took off and completed - as fast as any copy operation has ever completed on this Windows 8.1 guest. It's as though the Windows Networking protocol stack doesn't know how to keep itself stimulated to continue copying without piggybacking on packets being pushed through by another operation.
Log file after the session in which I did the above:
http://Noel.ProDigitalSoftware.com/temp/VMware.log
Let me know if you'd like me to turn on more verbosity and capture another log.
-Noel
