I had the exact ssme thing happen on my 03' and after trying several diffrent things it came down to this
http://cgi.ebay.com/ebaymotors/AC-He...Q5fAccessories
i wish i would have known in the begining because it takes all of 15 min to change
and if you find a leak under the passenger side carpet IT IS NOT THE HEATER COIL! DO NOT TAKE YOUR DASH APART! you will find that the drain hose on the passenger side firewall is behind a heat shield and it tends to blow back in on the outside of that hose, just bend out the heat shield a little and coat arount that hose with some 5200 sealant it should save you a couple of days trying to get the dash out to get to everything else