Thanks.
It seems to use the normal SPI library and the problem with that is that it is talking directly to the hardware registers of the processor. On the Due those registers are simply not present in the same location with the same bit meanings.
To further complecate the matter the Due's SPI pins are not on the same pins as a normal Arduino but are on a pin header, the one just above the Arduino Logo.
So the whole thing needs a bit of a rewrite I am afraid. That is the problem with libraries that talk direct to hardware, when the hardware changes the rug is pulled from underneath it.