There seems to be a bug when validating several rows against rows returned from the database.
 
This did not work:
 
<Columns>

      <msgLogDescription isUnique="true">xxxxx</msgLogDescription>
      <statusId>1</statusId>
    </Columns>

 
It did not match against the database. I modified the method: DBRowToValidate.AddUniqueCell from
 
public void AddUniqueCell(DBCellToValidate cell)

    {
        ArgumentValidation.CheckForNullReference(cell, "cell");
          this.cells.Add(cell);
    }

 
to this:
 

  public void AddUniqueCell(DBCellToValidate cell)
    {
        ArgumentValidation.CheckForNullReference(cell, "cell");
        uniqueCell = cell;
        this.cells.Add(cell);
    }

 
and everything worked as expected.
 
public void AddUniqueCell(DBCellToValidate cell)

    {
        ArgumentValidation.CheckForNullReference(cell, "cell");
        uniqueCell = cell;
        this.cells.Add(cell);
    }

 
and everything worked as expected.