UDO problems

Hi, I've just started experimenting with UDO.

I created to tables SM_OTest and SM_OTest1. I added an alphanumeric(20) field to the header table and two alphanumeric(20) fields to the rows. I registered the UDO and allowed the system to create a default form.

When I open the form and try to add, I get the following error:

"Error Converting Data Type nvarchar to int (CINF)"

Why does it do this?