Girlfriend's 99 Jetta had a weird streak running through the rear view mirror last week... sort of cloudy for 1/3 of the mirror and hard to see through. Today she calls while driving it to say that some green liquid has been dripping down from it. What the heck do they put in their rear view mirrors anyhow? Is this a common problem? I suppose the fix is just replacing the thing but now I'm curious what the liquid is/does.