1998 Lincoln Town Car Interior leak

I bought a 1998 Lincoln Town Car in October 2009. It had been kept in a garage by its first owners and not subjected to the elements unless they were actually driving in "weather". I discovered not long after that the interior was taking on water every time it rained. I took it to a mechanic who said they blew out the drain lines (which had been blocked) from the sunroof and that the problem should be fixed. Because it had not rained a great deal after that, I thought the problem was gone. It wasn't. I wound up taking the vehicle to another mechanic who said they blew out different drain lines, also from the sunroof, and that the problem should be solved. While the water that has gotten inside my car recently is not nearly as much as before, the interior of my car on the passenger side, particularly in the backseat floor, is still damp and I'm very concerned about mold, in addition to wanting this problem to be fixed. Any ideas what might be contributing to this problem?