hmm this sounds exactly what i had when i first got my heap of shit car
the problem wasn't pretty so i hope this isn't the case for you but sounds like it might be, the only difference was that mine was on the passenger side A pillar. i also thought it might be the sunroof drainage pipes (which do go through the A pillar) but they were soon eliminated from the problem list. just poor some water around the sunroof (while open so be careful), and watch the water drip out the bottom of the car, hard to explain where, but they pop out straight between the bottom of the door (the hinges side) and the fender.
in my case this was the problem:
it was all fixed in the end, but the windshield had to be taken out and stuff. but in my car you could see a bit of outside damage on top of the windshield, the rubber stripping was lifted up slightly.
anyway this was her in surgery:
good luck guys...
