Share 'Materials in AutoCAD Architecture 2013 objects not rendering'

Just installed AutoCAD Architecture 2013 and then the latest (April 2012) version of nXt but materials set within AutoCAD Architecture objects, like the wood of a door and the glass in windows, do not render correctly, they appear a default grey.   The Walkabout and AutoCAD shaded views of these objects look correct and this same file in AutoCAD Architecture 2012, with this same latest nXt update…