I have a dateTimePicker control placed on a standard SF Maintenance Form.  The dateTimePicker control is setup to clear on null when the value is 1/1/1800.  What is happening is when I use the Maintenance forms navigator and move to a record with a null value the dateTimePicker control displays a blank field which is correct but the navigator becomes grayed out and the MaintenanceFormToolStrip only allows New, Edit or Delete to be selected.  I'm unsure of why the navigator becomes grayed out.

Same problem I'm having... Let me know if you found a solution. I don't want the underlying buffer to be dirty when I navigate and the get of the field behavior fires regardless of how the UI handles it.

This is the purpose of the NULL settings within the BO Mapper.  Create a Return Alternate Value on NULL value and set the return value to #1/1/1800# and then rebuild the partial.  So when there is a date value that is null, the BO property will return #1/1/1800# and it will be treated as a NULL by the DateTimePicker.