title: Have issue with typed dataset nullable date value
body: <p>I have a <code>datatable</code> in a typed dataset with a date column
  When I change the <code>NullValue</code> property to return <code>null</code> or <code>empty</code> , vs 2008 wont let me.</p>
  
  <p>it says</p>
  
  <blockquote>
    <p>The value entered is not valid for the current data type.</p>
  </blockquote>
  
  <p>I need to be able to set null values por this column.</p>