I had a similar problem with a different car. You should check the water channels that allow water to flow from the windscreen.
The should be a couple of rubber drains coming from the plenum these can become blocked and allow wat to spill over to undersirable areas. Try poke through them with a wooden spoon.
If this is your problem you will know when you clear the blckage and a pint of crap flows out.
Carl, July 2012