simple mesh picking problem

Hi, i am trying to do picking with c#, but it dosent work. I basically converted the picking c++ sample to c# and managed directX, so here is my code.

Microsoft.DirectX.Direct3D.IntersectInformation hitInfo = new Microsoft.DirectX.Direct3D.IntersectInformation();	

			

			foreach ( Piece piece in mChessForm.Board.WhitePieces )
			{
				System.Drawing.Point ptCursor = System.Windows.Forms.Cursor.Position;	

				Microsoft.DirectX.Matrix matProj = mChessForm.Renderer.Device.Transform.Projection;
				Microsoft.DirectX.Matrix matView = mChessForm.Renderer.Device.Transform.View;
				Microsoft.DirectX.Matrix matWorld = piece.WorldMatrix;

				// Compute the vector of the pick ray in screen space

				Microsoft.DirectX.Vector3 v = new Microsoft.DirectX.Vector3();				
				v.X =  ( ( ( 2.0f * ptCursor.X ) / mChessForm.Renderer.Device.Viewport.Width  ) - 1 ) / matProj.M11;
				v.Y = -( ( ( 2.0f * ptCursor.Y ) / mChessForm.Renderer.Device.Viewport.Height ) - 1 ) / matProj.M22;
				v.Z =  1.0f;

				Microsoft.DirectX.Matrix m = matWorld * matView;
				m.Invert();

				Microsoft.DirectX.Vector3 vPickRayDir = new Microsoft.DirectX.Vector3();
				Microsoft.DirectX.Vector3 vPickRayOrig = new Microsoft.DirectX.Vector3();
	
				// Transform the screen space pick ray into 3D space

				vPickRayDir.X  = v.X*m.M11 + v.Y*m.M21 + v.Z*m.M31;
				vPickRayDir.Y  = v.X*m.M12 + v.Y*m.M22 + v.Z*m.M32;
				vPickRayDir.Z  = v.X*m.M13 + v.Y*m.M23 + v.Z*m.M33;
				vPickRayOrig.X = m.M41;
				vPickRayOrig.Y = m.M42;
				vPickRayOrig.Z = m.M43;

				if ( piece.Model.Model.Intersect ( new Microsoft.DirectX.Vector3(0,0,0), vPickRayDir, ref hitInfo ) == true)
				{
					System.Windows.Forms.MessageBox.Show(piece.ToString());
				}

			}

if someone can help me with this, ill be gratefull thanx