Hello Jeff,
there are two APIs for NI-CAN, the channel API and the frame API. The DIAdem driver for NI-CAN is based on the channel API of NI-CAN. Unfortunatelly this API is not supported by the USB-CAN modules. These modules support only the frame API of NI-CAN. Thus DIAdem does not support the USB-CAN modules.
Unfortunatelly in MAX you can assign a CAN message to a USB-CAN port so that you might think everything is fine with this setup. But if you launch the Testpanel, you will see that you cannot run it on the USB-CAN ports.
Rainer