Shader gone wrong

Hallo everyone.
I just ported my project form 3.5 to 4.2 and it looks like my shader is doing weird things.

What the shader should do: reflective - > Qubemap with rim fallof
What it does : Shows the world norma.

Is there anything changed in the shader code that this shader breaks?
Thanks for any hints or tips.

Code (csharp):

1.  
2. Shader "Capture/QubeMap Reflection Vertex Lit" {
3.     Properties {  
4.       _Color ("Main Color, Alpha", Color) = (1,1,1,1)
5.       _MainTex ("Texture", 2D) = "white" {}  
6.       _Cube ("Cubemap", CUBE) = "" {}
7.       _Reflection ("Rim Power", Range(0,1)) = 1
8.     }  
9.     SubShader {  
10.       Tags { "RenderType" = "Opaque" "LightMode" = "Vertex" }  
11.       CGPROGRAM  
12.       #pragma surface surf Lambert  
13.       struct Input {  
14.           float2 uv_MainTex;  
15.           float3 worldRefl;
16.           float3 viewDir;
17.       };  
18.       sampler2D _MainTex;  
19.       samplerCUBE _Cube;
20.       float _Reflection;
21.       float4 _Color;
22.       void surf (Input IN, inout SurfaceOutput o) {  
23.           o.Albedo = tex2D (_MainTex, IN.uv_MainTex).rgb * 0.5;
24.           o.Albedo *= _Color.rgb;
25.           o.Emission = _Reflection * texCUBE (_Cube , IN.worldRefl).rgb;
26.       }  
27.       ENDCG  
28.     }  
29.     Fallback "Diffuse"  
30. }