I also had the same problem (also same year car). Without having to take the headliner down (pain!), first thing you should do is check the actual drain openings in the sunroof. There are four of them in each corner (or near each corner) of the sunroof. This thread, has some pictures of the front holes:
http://forums.genvibe.com/zerothread?id=42749. Just open the sunroof and stick your head up there-you'll see them! There might be junk or something clogging them up there. If they look clear, then I suggest on a dry day, pouring a cup of water in each corner to see if the water is actually draining out of the drains. If they are then you should have four wet spots under your car, kinda near each tire (you can see the drain openings under the car like in that previous link). That way you can tell which drain specifically is giving you problems.Before I did that I tried blowing compressed air in the drain holes in the sunroof. I had my mechanic to do it when I had my oil drained. But that didn't work anyways, for me at least. Then I discovered that one of drainage tubes was actually kinked, not allowing the water to drain. Check out this thread for what I did there:
http://forums.genvibe.com/zerothread?id=25645 Good luck!PS- You haven't had your windshield replaced recently have you? Just wondering 'cause mine was replaced right before I bought mine and they did it wrong and it was leaking from there once too (besides the sunroof problem).