Drag and drop rows within the same datagridview

Hi

I have a datagrid with multiselect enabled and I want allow the user to order rows by drag and drop.

I found code from anotehr question in the form:  http://social.msdn.microsoft.com/Forums/windows/en-US/16b0a44e-35a0-4bc8-9ccd-ec2c62c95a55/select-and-drag-a-datagridview-row-with-a-single-click

but it's doesn't works for me - I success to drag but not to drop, it's show me "now allow" icon like i draw here:

Image may be NSFW.
Clik here to view.

the full drag and drop code is:

// Aid variables
private Rectangle dragBoxFromMouseDown;
private int rowIndexFromMouseDown;
private int rowIndexOfItemUnderMouseToDrop;

private void dg_MIX_MouseMove(object sender, MouseEventArgs e)
{
	if ((e.Button & MouseButtons.Right) == MouseButtons.Right)
	{
		// If the mouse moves outside the rectangle, start the drag.
		if (dragBoxFromMouseDown != Rectangle.Empty &&
			!dragBoxFromMouseDown.Contains(e.X, e.Y))
		{
			// Proceed with the drag and drop, passing in the list item.    
			DragDropEffects dropEffect = dg_MIX.DoDragDrop(
			dg_MIX.Rows[rowIndexFromMouseDown],
			DragDropEffects.Move);
		}
	}
}

private void dg_MIX_MouseDown(object sender, MouseEventArgs e)
{

	// Get the index of the item the mouse is below.
	rowIndexFromMouseDown = dg_MIX.HitTest(e.X, e.Y).RowIndex;
	if (rowIndexFromMouseDown != -1)
	{
		// Remember the point where the mouse down occurred. 
		// The DragSize indicates the size that the mouse can move 
		// before a drag event should be started.                
		Size dragSize = SystemInformation.DragSize;

		// Create a rectangle using the DragSize, with the mouse position being
		// at the center of the rectangle.
		dragBoxFromMouseDown = new Rectangle(new Point(e.X - (dragSize.Width / 2),
													   e.Y - (dragSize.Height / 2)),
							dragSize);
	}
	else
		// Reset the rectangle if the mouse is not over an item in the ListBox.
		dragBoxFromMouseDown = Rectangle.Empty;
}

private void dg_MIX_DragOver(object sender, DragEventArgs e)
{
	e.Effect = DragDropEffects.Move;
}

private void dg_MIX_DragDrop(object sender, DragEventArgs e)
{
	// The mouse locations are relative to the screen, so they must be 
	// converted to client coordinates.
	Point clientPoint = dg_MIX.PointToClient(new Point(e.X, e.Y));

	// Get the row index of the item the mouse is below. 
	rowIndexOfItemUnderMouseToDrop =
		dg_MIX.HitTest(clientPoint.X, clientPoint.Y).RowIndex;

	// If the drag operation was a move then remove and insert the row.
	if (e.Effect == DragDropEffects.Move)
	{
		DataGridViewRow rowToMove = e.Data.GetData(
			typeof(DataGridViewRow)) as DataGridViewRow;
		dg_MIX.Rows.RemoveAt(rowIndexFromMouseDown);
		dg_MIX.Rows.Insert(rowIndexOfItemUnderMouseToDrop, rowToMove);
	}
}

Does someone know why I get this error icon and how can I improve the code to supported multi line select?

Thank you !