David & Marcus:
Thank you for your comments and especially for clarifying the use of wait windows in debugging an exe. I will remember that.
As it happens, I found the source of the problem by recreating a critical business object that lay at the heart of a number of form objects. It fixed the problem.
Why couldn't I have done that yesterday, or the day before 8-)
Many thanks
Godfrey
Godfrey Nicholson
Ofek Technologies Ltd
Auckland
New Zealand