DrawIndexedPrimitive problem

      
typedef struct
{

	float x, y, z, rhw;
	DWORD color;

}GUICUSTOMVERTEX;
  

-> Initcode
      
		_x = 1;
		_y = 1;
		_width = 500;
		_height = 500;

		GUICUSTOMVERTEX		verts[] = { {(float)_x, (float)_y, 0.5f, 1.0f, 0xffffffff},
										{(float)(_x+_width), (float)_y, 0.5f, 1.0f, 0xffffffff},
										{(float)(_x+_width), (float)(_y+_height), 0.5f, 1.0f, 0xffffffff}, 
										{(float)_x, (float)(_y+_height), 0.5f, 1.0f, 0xffffffff } };
		DWORD				indic[] = { 0, 1, 2, 0, 2, 3 };
		DWORD				dwSizeVerts = sizeof(verts);
		DWORD				dwSizeInd = sizeof(indic);
		
		// create vertex buffer:

		if ( FAILED ( m_d3dDevice->CreateVertexBuffer( dwSizeVerts, 0, dwCustomFVF, D3DPOOL_MANAGED, &m_lpVertices ) ) )
			return false;	// failed !

		// fill it with data

		VOID* pVertices;
		if( FAILED ( m_lpVertices->Lock ( 0, dwSizeVerts, (BYTE**)&pVertices, 0) ) )
			return false;
		memcpy ( pVertices, verts, dwSizeVerts );
		m_lpVertices->Unlock ();


		// create index buffer:

		if ( FAILED ( m_d3dDevice->CreateIndexBuffer( dwSizeInd, 0, D3DFMT_INDEX16, D3DPOOL_MANAGED, &m_lpIndices ) ) )
			return false;
		// fill it with data

		VOID* pIndices;
		if ( FAILED ( m_lpIndices->Lock(0, dwSizeInd, (BYTE**)&pIndices, 0 ) ) )
			return false;
		memcpy( pIndices, indic, dwSizeInd );
		m_lpIndices->Unlock();
  

->Drawing code
      
		m_d3dDevice->SetStreamSource( 0, m_lpVertices, sizeof(GUICUSTOMVERTEX) );
		m_d3dDevice->SetIndices( m_lpIndices, 0 );
		m_d3dDevice->SetVertexShader( D3DFVF_XYZRHW | D3DFVF_DIFFUSE );
		m_d3dDevice->DrawIndexedPrimitive( D3DPT_TRIANGLELIST, 0, 4, 0, 2);