The check box editor in RadGridView is a permanent editor and the cell value will be changed only when you change the current cell. To force changing the value when the user checks the check box, you need to subscribe to the ValueChanged event of RadGridView and call the EndEdit method:
void radGridView1_ValueChanged(object sender, EventArgs e)
{
if (radGridView1.CurrentColumn.Name == "MyCheckBoxColumnName")
{
radGridView1.EndEdit();
}
}