Heh, I forgot that I always put stuff in the /random folder... ^^;; Sorry.
I've been doing plugins for a while, it's just that they usually don't pan out so there's no point in releasing.
What I suspect is happening there is the cache gets blown, so that even though both paths lead back to the same addgrain'd clip, it gets done twice - but I might be entirely wrong. I'll take a look.