>When I got this error, I was not using a grid to add the record. I did have a grid on one tab for locating a desired record and a separate tab for >entering and editing data but I was not adding records directly to the grid. I don't know if that makes a difference or not.

I don't understand what you mean with "I was not adding records directly to the grid". Did you create a new entity? Are you using the NEW button?

You can try to step through the mmButtonsSave_Click()...

open the file C:\Program Files\Mere Mortals .NET Framework 2008\Mere Mortals Framework Windows Forms\Controls\mmButtonSave.cs and put a breakpoint on mmButtonSave_Click (on the bottom of the file)...