Shader execution stops in vertex shader before pixel shader

Question

I’m trying to store the depth information of model in XNA from the lights point of view. The model renders fine using a normal shader.

This is the shader code

float4x4 xShadowMapLight;


///DEPTH MAP

float4 RenderShadowMapPS( VS_SHADOW_OUTPUT In ) : COLOR
{ 

  return float4(1,0,0,0); //In.Depth.x,In.Depth.x,In.Depth.x,0);
}

VS_SHADOW_OUTPUT RenderShadowMapVS(float4 vPos: POSITION)
{ 
  VS_SHADOW_OUTPUT Out;

  Out.Position = mul(vPos, xShadowMapLight);

  Out.Depth.x = 1-(Out.Position.z/Out.Position.w);    
  return Out;
}


technique ToonShaderDepthMap
{

 pass P0
 {

   VertexShader = compile vs_2_0 RenderShadowMapVS(); 
   PixelShader = compile ps_2_0 RenderShadowMapPS();
 }

}

And this is the way I generate the light matrix that is passed to the shader.

 Matrix view = Matrix.CreateLookAt(modelTransform.Translation, new Vector3(0, 500, 75), Vector3.Up);
 Matrix projection = Matrix.CreatePerspectiveFieldOfView(MathHelper.PiOver4, 1.0f, (float)globals.NEAR_PLANE, (float)globals.FAR_PLANE);
 Matrix ShadowMapLight = modelTransform * view * projection;

But apparently I’m not always getting to the pixel shader and it stops in the vertex for some reason. (I have modified the pixel shader to output always a red pixel, so I know when it goes through).

xShadowMapLight is the Matrix containing all the transformations from the lights point of view. Apparently the problem is in mul(vPos, xShadowMapLight); cause if I change the matrix for an Identity one the shader gets to the pixel one.

Any idea why this might happen?