Thanks for the reply!
I read both "Setting Default Values in New Rows" and "Working with Typed DataSets" topics in the MM.NET Dev Guide. Neither really addresses my immediate problem.

I successfully create a new blank row (except for the ID which comes via SQL Identity) via the mmNewUltraButton.
I then key all the other fields values (thus no defaults should be needed).
I either press a mmSaveUltraButton or navigate to a different record via Previous or First navigation buttons and the corresponding click event code line Me.oVisitorType.SaveRow() generates the error.

I seem to be missing why the values keyed into the control are not being updated into the dataset prior to the SaveRow method being called. Am I missing a step? How do I update the data row prior to calling the SaveRow method?

MANY MANY THANKS!!!!