Hi Elmo, 
The problem is not the hardware.  The two drivers cannot be installed together.  You can only have NI-CAN or NI-DNET, not both. 
At the moment there is no easy workaround.  You mention using NI-CAN to implement DNET.  This is possible, but you need the DNET specification to interpret the frames according to the DNET spec. 
DiegoF
National Instruments.