Darned if I can figure out what I did. I can't make it happen again. What I THOUGHT I did was this:
Created a new TCP server device named Fred
While still in the device creation dialog, noticed that I had made it a server.
Delete and recreate as a TCP Client.
At some point, when exiting the Device Config dialog, I think, I was warned that there was an orphaned heap item which would now be renamed to 'aFred' or something like that.
The recreated device showed as a client, which was the one that wouldn't open.
As soon as I created a new device from scratch with a new name, it immediately was able to connect (sure of this step)
So, for one thing, I don't think there was ever any ladder that addressed Fred while it was configured as a server.