VB .Net and Datasets

Hi Experts,

  I have a combobox control  that have a datasource created with the datasource wizard and basiccly is:

SELECT DISTINCT '-Seleccione-' As Login FROM CMS
Union All
SELECT Distinct rtrim(Login) FROM CMS WHERE Convert(Smalldatetime,Fecha,103) Between Convert(Smalldatetime,@FechaI,103) And Convert(Smalldatetime,@FechaF,103) Order By login Desc

After i call
CMSTableAdapter.Fill(Db_AsistenciaDataSet.CMS, Format(DateTimePicker1.Value, "dd/MM/yyyy"), Format(DateTimePicker2.Value, "dd/MM/yyyy"))
An exception is  thrown telling me:
Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints
But the dataset is filled (The combobox is filled).

Any idea
Thanks


        CMSTableAdapter.Fill(Db_AsistenciaDataSet.CMS, Format(DateTimePicker1.Value, "dd/MM/yyyy"), Format(DateTimePicker2.Value, "dd/MM/yyyy"))

An exception is theown telling me that:

Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints

But the combobox is filled.

Any idea?
Thanks