Hi Rob

Thank you for responding.  I deleted my original post because it was a "wood for trees" situation.  I was getting some very spurious results and, clutching at straws, thought the size of the param definitions was somehow indicative of the source of them.  It seems that this is not necessarily the case and is nothing to sweat about.

My problem turned out to be a group of parambyname's which somehow had a rogue fieldbyname parameter in the midst of it.  It took me over a day to find that typo.  Aaaargh.