i had exactly the same problem with my 1.4 rt, with electric factory fit sunroof. turns out water was not coming through the seals around the glass, but past the black mouldings on the roof which surround the sunroof and 'hold it in place'. by the time we found this out the sensor for the remote key was fried, but i replaced this for £40 at a renault dealer, got my dad to re-seal around the roof with black exterior seal and the roof has been water tight ever since. just make sure that you crush the tip of the sealant with pliers to avoid staining to the paintwork on your roof. hope this is helpful!
Phil Allman, July 2007