Andrew,
What version driver do you have installed on this computer? For the virtual hub to be detected in the software it requires the latest version driver (5.7.25).
To update the driver, disconnect all Promethean hardware from the computer, remove/ uninstall the ActivDriver and restart the computer. You can install the latest version driver from the link below.
www.prometheanplanet.com/.../ProductPage.aspx
Thanks!