Shader error: too many "TEXCOORD"

I wrote a surface shader that's an extension to the bumped diffuse shader (ads snow based on world normal). that worked, then I made a variant with specular, but that doesn't compile. I get the error:

Shader error in 'Custom/snowBumpedSpec': Program 'frag_surf', input semantic attribute "TEXCOORD" has too big of a numeric index (8) at line 74 Keywords: DIRECTIONAL, LIGHTMAP_OFF, DIRLIGHTMAP_OFF, SHADOWS_SCREEN

So apparently I use to many texcoord, which doesn't make much sense to me, as I don't use more than in my (snow) bumped diffuse shader.

Also, I looked at the built in Reflective/Bumped Specular shader, and it's just as complex; the same amount of textures, the same amount of parameters, and even 1 more uv-set (1 use the float2 uv_MainTex for both the diffuse and normalmap)

So anyone that can help me ?

Edit: the shader:

 Properties 
     {
  _MainColor ("Color", Color) = (1,1,1,1)
  _MainTex ("Texture", 2D) = "white" {}
  _SpecColor ("Specular Color", Color) = (0.5,0.5,0.5,1)
  _Shininess ("Shininess", Range (0.01, 1)) = 0.078125
  _BumpMap ("Bumpmap", 2D) = "bump" {}
  _SnowTex ("Snow", 2D) = "white" {}
  _SnowAmount ("Snow Amount", Range(0.0,5.0)) = 1.0
     }
     
     SubShader 
     {
       Tags { "RenderType" = "Opaque" }
       
       CGPROGRAM
       #pragma surface surf BlinnPhong
       #pragma target 3.0
       
       struct Input 
       {
           float2 uv_MainTex;//:TEXCOORD0;
           //float2 uv_BumpMap;
           float3 worldPos;
           float3 worldNormal;
  INTERNAL_DATA
       };
       
       float4 _MainColor;
       sampler2D _MainTex;
  float _Shininess;
       sampler2D _BumpMap;
       sampler2D _SnowTex;
       float _SnowAmount;
       
  void surf (Input IN, inout SurfaceOutput o) 
  {
         float4 tex = tex2D (_MainTex, IN.uv_MainTex)*_MainColor;
         float4 snow = tex2D (_SnowTex, IN.worldPos.xz);
         o.Normal = UnpackNormal (tex2D (_BumpMap, IN.uv_MainTex));           

         float snowfactor = 1 - WorldNormalVector(IN, normalize(o.Normal)).y;
         snowfactor = snow.a - snowfactor;
        
         if (_SnowAmount>1)
             snowfactor *= _SnowAmount;
         else
             snowfactor += (_SnowAmount-1)*2;
         snowfactor = saturate(snowfactor);
         tex = snow*snowfactor + tex*(1-snowfactor);
         o.Albedo = tex.rgb;
         o.Specular = _Shininess;
         o.Gloss = tex.a;
         o.Alpha = tex.a;
  }
       ENDCG
     } 
     
     Fallback "snowSpecular"

Edit2: the compiled shader:

 Shader "Custom/snowBumpedSpec" 
 {
     Properties 
     {
  _MainColor ("Color", Color) = (1,1,1,1)
  _MainTex ("Texture", 2D) = "white" {}
  _SpecColor ("Specular Color", Color) = (0.5,0.5,0.5,1)
  _Shininess ("Shininess", Range (0.01, 1)) = 0.078125
  _BumpMap ("Bumpmap", 2D) = "bump" {}
  _SnowTex ("Snow", 2D) = "white" {}
  _SnowAmount ("Snow Amount", Range(0.0,5.0)) = 1.0
     }
     
     SubShader 
     {
       Tags { "RenderType" = "Opaque" }
       
       // surface shader with errors was here
 Pass { }
 /*/* surface debug info:
  needs world normal vector
  needs world space position
  stuff performed in tangent space
  passes tangent-to-world matrix to pixel shader
 */
 /* surface debug info:
  needs world normal vector
  needs world space position
  stuff performed in tangent space
  passes tangent-to-world matrix to pixel shader
 */
 /* surface debug info:
  stuff performed in tangent space
 */
 /* surface debug info:
  needs world normal vector
  needs world space position
  stuff performed in tangent space
  passes tangent-to-world matrix to pixel shader
 */
 */
 #LINE 65
 
     } 
     
     Fallback "snowSpecular"
   }