I remeber etlsport posting about how his windshield gasket was leaking. By the time it started letting water in, he had significant rust behind the gasket. Get your local windshield shop to inspect your seal to see if they can determine if that is where the leak is coming from. If the seal is bad, you'll have to plan on taking it to a body shop to get the rust taken care of before re-install.

I also seem to remember that some members found a leak through the firewall that was easily fixed by some sealant.

Have you just been searching on 'wet carpet' or have you also tried to search on 'windshield leak'?