OK. I have re-installed the IDE from a fresh download and the Ethernet sketch now compiles and uploads perfectly. Therefore I can only assume that the libraries that were installed as part of my first original ( 1.0 ) installation were not compatible with the upgrade to the latest IDE 1.0
However, I did have a problem with another sketch that uses the Dallas Temperature library. Had to make a change to the .cpp file as reply#5 here :
to zoomkat, my sincere thanks for the assistance.