Shader bug or feature?

I found a shader in forums that makes an invisible object cast a shadow. Works great in version 4, doesn't work in version 5. In 5 the object just appears purple. The shader code itself is very short so I was wondering if somebody who knows shaders better could tell what the problem is. Is this a bug in version 5 or something that is no longer supported?

Code (CSharp):

1. Shader "Transparent/InvisibleShadowCaster"
2. {
3.      Subshader
4.      {
5.          UsePass "VertexLit/SHADOWCOLLECTOR"  
6.          UsePass "VertexLit/SHADOWCASTER"
7.      }
8.      Fallback off
9. }