Solved! Well in a fashion anyway.
I've just plugged in a new Samsung 19" TFT monitor and updated the monitor driver, the right click problem has now gone.
I can only think that the problem was the driver for my old GNR 17" CRT monitor (CM1772FS)?
According to the info from the .inf file, the driver on the disc suppied with the monitor was released in March 2002 (ver 0.3).
Strangely, the .inf file available from http://www.gnr.co.uk/
was released on August 2001 (ver 0.1)?
Neither drivers solved the problem.
Make of this what you will, its unlikely i'll return to my old GNR monitor, I hope its of some use to anyone with the problem.