Specific message received: Display Link has detected USB graphics software installed from a different vendor. This software is not compatible with DisplayLink USB graphics software and must be uninstalled before DisplayLink Software can be installed.
This then links to this page:
http://displaylink.com/support/ticket.php?id=359
And I've followed all the instructions there. The four noted programs on that page were not on my system. I did have a StarTech USB program that I had used for a device to convert VGA to USB for projector use - and I did uninstall that just in case.