I think we're coming to the conclusion that FTM is one of those programs that A) works very differently (from perfectly to not at all!) on a variety of platforms (type of computer, variety and version of operating system) and B) has an equally wide range of difficulty in coping with network connections.

I suspect it is highly sensitive to what else is installed on any given machine, too, apart from the obvious usual suspects (anti-virus and firewall settings), which have been blamed for such things for too long now. For absolutely no apparent reason, mine has "bad days", when it just crashes itself when asked to sync - or even just decide who's married to who! Other days it's all smoothness. Ho, hum ...