I've had my Droid X for about a month, so I'm familiar with how it works. Two days ago, I could make and receive calls, but there was no Voice communication. I would dial a number, and it looked like it was working OK, but I never heard anything - not even the other phone ringing. When someone called me, the phone would ring, and I'd answer it. I couldn't hear the caller, and he couldn't hear me.
I tried it from 9:00 a.m. till about 10:00 p.m., using my home phone. The call would go through in either direction, but there was no voice reception in either phone. I did not even hear the ringing noise in the earpiece of the Droid when I called a number.
Yesterday, it worked fine. Maybe I should have turned it off and let it reboot. I asked at the Verizon store, and they had never heard of that happening.