Microsoft's Bug:

If you are populating a DataGrid in your Windows Forms application and are
using a TableStyle to define custom columns, you will not get a
DataGridBoolColumn to correctly save or retrieve boolean values from your
DataSet. This will occur IF you manually set the TrueValue and FalseValue
properties of the DataGridBoolColumn object in the designer explicitly. This
occurs because the designer will convert whetever you type in those two
properties to System.String values - not System.Boolean values.

You should explicitly set the TrueValue and FalseValue properties of the
DataGridBoolColumn object to actual boolean values as shown below.
    private void frmMyForm_Dates_Load(object sender, System.EventArgs e)
    {
        // other Loading event code ....

        // This is what the VS.NET designer does:
        dataGridBoolColumn1.TrueValue = "True";
        dataGridBoolColumn1.FalseValue = "False";
        // The preceding causes a problem because the DataSet Column used with
this
        // column is of type System.Boolean and NOT System.String.

        // So, change it to something like the following to fix the problem:
        dataGridBoolColumn1.TrueValue = true;
        dataGridBoolColumn1.FalseValue = false;
    }