We have the same problem, and we have yet to resolve it! It is coming from somewhere high up under the dash, behind the emergency brake. One thing to try (you'll need two people) is to pour a controled amount of water in to the area where you can see the water should be channeled (I also used the same method to check the sunroof). If you have the hood up, you can see the channels lead to the area beside the hood springs. I use a watering can with a long narrow spout so I can control the exact spot. Pour water in there and see if it comes inside the cabin. It does on our car. It's difficult to fix because you have to be careful not to plug the drain, so you can't do a blanket type patch (which would be useful when you don't know the exact spot). We have tried fixing it from the outside adn the inside, and our next step is to remove the emergency brake and try again from the inside (higher up).
In the meantime, I have one of those Dri-somethings that accumulates the water in to a bucket using a salt. Works quite well. I also try to either park under cover, or if that isn't an option, with the car sloping towards the passenger side. THis helps a LOT.
If you figure it out exactly, let me know too, okay?!
