Hello Ric,
Strange. Can you install RealBand to a new folder like C:\rb_test and run it from there to see if you get the same error with a fresh install? You can choose to install only RealBand during the BB installation. Or if you have a PG hard drive, run the setup and choose the custom option.
Make sure to plug the interface in before starting RealBand. Let us know how that goes.