Vapor barrier seal leak. Been there, done that. Go to the dealer and buy a roll of the the 3M rubber sealer tape/rubber gummy stuff.
Now, here is the easiest way to fix this. First, spray the door, window and seals and get everything wet with your garden hose. Open and check the door jam, there should be some water in there, that is good, now you can trace the source. Remove the door panel, and rather than remove and completely reseal the vapor barrier, simply look around and find the places where it is leaking, you may need a drop light or flashlight to see clearly. Then, when you find a leak, tear a long peice of the tape (at least two or three inches longer than the area affected, and work it into the seam/seal and squish it down under the foam vapor barrier real good. Use your thumbs to press hard and smooth it out. Do this everywhere you see water or wetness. While you are at it, wet and inspect your other doors, you will probably find them leaking, though not enough to cause water on your floor, but if there is water at the bottom of the door jam, that is bad! Fix it. The dealer would completely remove the vapor barrier and reseal, and they were not 100% sucessful, but I did my "patching" method and had better sucess.