One has XP SP2, the other XP SP3.
On the XP SP2 computer, it works; connects, commander appears, I can copy files.
On the XP SP3 computer, it will connect, but after connection the screen does not appear.
The commander window doesn't appear, and there is a WinSCP process running but it has no UI.
I have to terminate it with task manager.
So it seems to be something that is specific to my XP SP3 computer.
Perhaps an interaction with other installed libraries, or IE configuration.
What can I do to help narrow this down?