Thanks for getting back.
The .CHM didn't run, got deleted, C3 doc's re-installed. Same error.
I've had problems with W10 and help files already, but I don't think that's what's up here.
Perhaps, some wierd W10 permissions thing? I'll check properties on the just installed file that doesn't work.
Sys (today's anyway): W10, Haswell-6 at 3.3, 16GB, etc., SSD-120GB for C:, TB's elsewhere
Network: HW Fiber connect to PC via ethernet, so I don't think there are problems there. And I'm obviously connected, just to be a wise guy.
I'll check the preferences stuff and get back.