I have only experianced this one time, and it was during our trip in a blizzard through WV just before Christmas. The water was dripping from right where you are saying. Off of the clip that holds the visor up, and only on the drivers side. I couldn't tell what was causing it, but i just figured it must have had something to do with all of the ice. Never saw it before, and haven't seen it since.
I too have the sunroof, so my be worth checking the drains like NVRDONE mentioned.