Weird Problem

Hi, I'm having a really weird issue. I'm using Daniel Brauer's pixelation effect shader from here

http://forum.unity3d.com/threads/183210-Making-a-local-pixelation-image-effect-shader

The shader works well and fits my needs. The only problem is that if I exit the unity editor or switch projects and come back again the shader doesn't seem to work anymore. The only way to fix it is to delete the shader asset and then drag it in again. Could this be a .meta file thing(I have VersionControl enabled)?

Any help is appreciated.

Thanks