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!
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