I had the same thing happen to me 3 or 4 times in my NAV equipped TCH. I haven't had time to check into it and mostly had dismissed it as a quirk, sort of in the same sense as the voice command not working very well. The first time this happened, I thought I had also lost the first call. I found the "transfer" button on the NAV telephone page and pushed it. I didn't get anything over my TCH/Bluetooth speaker but when I checked my cell phone itself, I still had my first call active on it and finished the conversation. I haven't had the telephone page up in any of the incidents since, as I have been manually going back to the NAV Consumption page during the course of my phone calls, so I couldn't depress a "transfer" button. I'll be interested to hear more about this, especially if there's a software fix, etc. similar maybe to Microsoft or Word updates or patches on my home computer.