Join Date: Feb 2009
Location: Brick, New Jersey
Not sure how much or how to tackle it but I had that problem with my 08 coupe. After taking it back to the place I bought it from found out that it was related to the sunroof drain tube was dislodged. It was fixed in less than an hour by the dealer under warranty. Not sure of how to fix it by yourself but hope this helps a little with debugging the possible other reasons why it is happening. You might have a crack in the tubbing too but mine was just it popped out of where it should be causing to leak down the I beam and getting the passenger seatbelt and seat wet.
Best of luck!
2008 Pontiac G6 GT Coupe Black
Performance: Hawk HPS Street brake pads
Appearance: HID Conversion Kit for Highs, Lows and Fogs 5000k, 5% 3M Window Tint, G6 Door Sills
Audio: Monsoon 200 Watt System
Future Mods: CRABS 03 with FPU, Racingline Strut Bar, Racingline MMI's, Continental Extreme Contact DWS Tires, Eibach Pro-Kit lowering springs, Power Slot Power Alloy Cryo-Treated Rotors