I had this problem on my 1999 VTR for a couple of years, didnt mind until it sent the central locking crazy. In the end I took the roof lining out and found it was the metal by the drain holes is a bad design and water has been literrally sitting there for probably all 11 years of its life, resulted in rusted hole therefor water getting in. In the end I took the sunroof out, chipped away the rust, used fibreglass underneath to sort the hole then used sealant to level it ouyt so the water actuallt went into the drainage tubes. Also check the tubes aint blocked up a mine where also. I then sealed around the sunroof, around the ariel hole and also around the windscreen to be safe. Problemo sorted!