DataTable.NewRow calls yield "Value was either too large or too smallfor an Int32"

I'm using typed dataset. The tables in the dataset have been filled from
the SQL Server.

The error happens when I go to work with a combo box. I need selected
DataRow for the combo, plus some phoney ones like "(new)" or "(all)".
What I do is create a List( of MyDataRowType ) and add the phoney ones
first, and then all from my DataTable. The error occurs when creating a
phoney one. But only for this one table. The same technique works elsewhere.

I wonder, could it have to do something with a BIT datatype used in this
table?

ANY hints or suggestions would be tremendously appreciated.