Sorry I know this is kinda old post but I have the same problem and I can't find what's wrong with my shader .. it's kinda complicated one.

Here is a link to it https://drive.google.com/open?id=0B88RRqRkmaeUWUpnUDAwbVlaRVU

and thanks in advance!

I have the same problem .. been working on a shader for hours now I'm totally stuck!