Maybe the configuration of my home network is funky. Image files are on an external hard drive on PC #1 and there is a thumbs database on each networked PC.
Build 3936 is too slow on networked PC #2 to test any functionality, I simply haven't the time to wait for TP to rebuild (or whatever it's doing) every directory every time I need access. I've rolled PC #2 back to Build 3935.
*** Response time on PC #1 is sufficient, I'll poke there.