I've noticed concurrent ORD sessions can only be run if ORD is loaded using "Open With" for files (vs using desktop icons) - is this intentional? Microstation Connect seems to have the same problem.
Try this ... right-click on the ORD icon and go to Properties. Once there, go to the Compatibility tab and enable "run as administrator".
Apply the changes and then try running multiple sessions again. Let me know what happens.