John - There are two answers here already. One, that worked for me, is to replace the dock connector at the bottom of the phone. The other, that worked for Trilaphis, is to open it up and blow out the earphone jack. Give those a shot.

Sasa - No, I'm afraid I don't know. It could be anything from static electricity having shorted something out, to that gold prong I described above not making contact anymore. It's even possible you had it in your pocket with a thumbtack or a metal shaving from something having rubbed off, and it got stuck. Mine was doing it when I bought it, so I haven't a clue. I just know that $20 in parts and an afternoon in work and I got it all working. What kind of water damage? Do you know what happened? Have you tried charging it from a wall charger and a computer? Cheers.

Trey - Is the antenna a seperate module? I don't see it listed on the ifixit parts listings. That won't require a complete logic board replacement? Cheers.

My wife's phone (a 3g 16gb) is having the same issue - the "gsm buzz" during calls. Sounds like a speaker when you hold a phone next to it while you're getting a text message. Except it's on the phone itself while you're making a call, and it's drowning out my voice. Me personally, I only sometimes hear it on my end, but the other end of the line (whoever we're talking to) says it's sometimes not there, sometimes there but not a big deal, and other times they can't hear anything but the buzz. Pretty consistently, if she gives it a good shake, or thumps it in her hand (holds the phone in one hand, and bumps her hand "vigorously" with the other, not thwacking the phone against the table) the buzz goes away for a while. I've done some more digging around. Many have suggested rebooting/restoring/reflashing the phone. It doesn't work (at least, it didn't work for me, and most other threads that said "Try a restore" didn't report any success). I restored to 3.1.2, then upgraded the baseband, and the bootloader, and...