According to this:
It is saying that the client doesn't have permissions for a socket. A couple of things to try:
-See if you are trying to make an active connection. Active and Passive FTP Transfers Defined An active connection needs to listen on a local port, and you may not have permission to do that. Switching to a passive connection might need fewer permissions.
-Disable local firewall or add an exception
-Run client as admin (in case out going requests are locked down)
-See if any other programs are monopolizing the ports on the machine (especially if run in active mode)
Thanks for the list.
I had already tried running in Admin, Unsuccessfully.
It is the firewall. Norton 360 is particularly finicky about permissions, and the upgrade triggered what had been permitted into not being permitted. An explicit OK was enough!