There is another thread on this here ..http://www.howtomendit.com/answers.php?id=110393
I have the same problem on an 05 only aware of it two days ago.
Karen
May 2012
take the panel off in front of screen and behind the battery in the bulkhead is the heater air pickup .it may be blocked in the drain down the side with leaves or dirt and the pickup has very low sides so a lot of rain and it cannot get away quick so it runs in the car.also in the bottom of the door are small holes to let water out that runs in down the window make sure it runs out there and not into car