When defining the MS_OPENV7 variable in the msconfig.cfg and thenopening another workspace the variable is being overwritten.
Defining the variable in the Standards.cfg file allowed the variable to be set regardless of what workspace is chosen.
Note also the comment in the msconfig.cfg :-
# >>>>> WARNING WARNING WARNING WARNING WARNING WARNING <<<<<## This file should never be changed by users! Any changes to the# configuration should be made in one of the files included by this# file.#