While I can't recall specifically using the CDC driver for the B1 Xplained board, I have used the one(s) for the Xmega A1 Xplained and the Xmega A3BU Xplained. I can't imagine there is much difference between them.
When I tried installing the CDC driver for the B1 Xplained USB STDIO example today, I got the following. This is in a Windows 8.1 machine using Atmel Studio 6 (Version: 6.1.2730 - Service Pack 2). Has anyone else had similar problems?
Do I need to turn Windows' paranoia level down?