Vertex Shader - Geometry vertex manipulation problem

I am trying to create a vertex shader that manipulates a mesh that I have. As a stripped down test, I found some code from codesampler that does geometry manipulation, in their case it makes a flag wave. In my case, it should flatten the geometry onto the y-plane. However the results are a little odd. I get two meshes, the vertex shader (white) and the original (orange)

img64.imageshack.us/i/testpfg.jpg/

Here is the code:

HLSL

#define IN_HLSL
#include "../shdrConsts.h"
#include "../hlslStructs.h"

struct outData
{
   float4 hpos : POSITION;   
};

outData main( VertexIn_PC In, uniform float4x4 modelView : register(VC_WORLD_PROJ))
{
   outData Out;

   float4 v = float4( In.pos.x, In.pos.y, In.pos.z, 1.0f );

   v.y  = sin( In.pos.x + 180.0f );
   v.y += sin( In.pos.z + 180.0f );
   v.y *= In.pos.x * 0.08f;

   Out.hpos = mul( modelView, v );

   return Out;
}

customMaterial.cs

singleton ShaderData(TestShaderData)
{
   DXVertexShaderFile     = "shaders/common/testShader.hlsl"; 
};

singleton CustomMaterial(TestMat)
{
   mapTo = "testmodel_tex";
   shader = TestShaderData;
   version = 2.0;
};