I had the same problem posted by "E46_M3Power" user (7/13/2011). I think I finally fixed it after 2 years of trial and error. First I tried the silicone bead across the front edge where the canvas meets the rubber. That did not stop the leak. Next I tried waterproofing the canvas top with 303 Fabric Guard which you should do annually anyway. That did not work. I checked that the drainage hole and channel that runs down the side of the windshield was not clogged. It wasn't. Here is what I did: I used a 1/4" solid piece of gray foam insulation, the same material that you'd use to wrap hot water pipes (see sample of foam next to a US dime). Insert a piece about 4 inches long into the support frame along side of the roof (in the pic, the end of the foam is seen).
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