open the sunroof, check the drainage hold in the front corners of the sunroof cavity...if they are ok, then check the seals for any damage or if they look old and worn, then i suggest getting some new ones... not mega expensive, and i know monkeyalan on here has the sunroof seal for sale if you pm him or look in the for sale section...
also check all the drainage lines ie the ones that run down the a-frame pillars on the outside (i jus aimed the jetwasher down them and gave them a blast, loads of stuff came out and problem solved...
if you do a search on here, im pretty sure there is a website with a guide to stop leaking, might be in the maintenence and info section pal.
hope that helps a tad.
rob