update
Ok- time for the 'daily' update:
We switched out my sim card yesterday. The techs and I didn't feel that was going to work, but we did it anyways. Well, it didn't work. The problem still exists. So as it stands, 2nd phone, 2nd battery, 2nd sim card, second memory card-- same problem.
We DID get somewhere with it afterwards though (hopefully).
Right after replacing the sim card and doing a complete reset-- As the phone puts you through the initial set up options, I approved the "verizon contacts synch" option, but couldn't approve the "google account setup/synch" immediately, as for some reason my password slipped my mind.
I did a soft reboot to correct the known sim card/text message error, so the phone was JUST reset AND restarted-- which normally means the problem won't occur for a while.
Five minutes later I was on the phone with someone WITHOUT the problem. Five minutes after that, I had my google password and reactivated the google account/synch on the phone. FIVE minutes after that I got a call and the problem occurred. Of course my friend and I called each other back and forth a few times and the problem persisted.
The tech and I talked a couple of hours later and of course we came to the decision to do a complete reset of the phone again, this time NOT reactivating my google account and just to be safe, not approving the Verizon contacts sych. Both of those options can be skipped upon initial phone reset.
I've gone through about 5 or 6 calls so far without a re-occurrence. We're obviously hoping the problem has something to do with the google account/synch. Bear in mind, turning the google sychs off completely in the phones synch settings- didn't work before. This is the first time trying the complete google account setup skip.
Hopefully the theory gets us somewhere, then its just a matter of determining why the google account is affecting only a few Thunderbolts in this way.
If anyone here would like to try the same thing in an effort to get more evidence, it would be great if they could report here on their findings.
Of course it's incredibly inconvenient to not set up the google account. You can't use marketplace, maps, gps, and a whole slew of other features on the phone without the google activation.
For anyone who wants to try. Here are a few things you may want to do first to make things easier:
First of all, a complete phone factory data reset (done under the SD card & phone storage option under the settings menu) should NOT tamper with apps, pictures and most other info STORED on your memory card. When you're doing the reset, it seems to suggest that info will be erased. It seems like only the installed information/apps are erased, but not anything backed up with a back up program, or copied to the card through a computer usb link previously.
Download a backup app from the marketplace, if you don't have one already. I use ASTRO. Backup your apps to the SD card. If you're afraid of losing your photos, back them up to your computer first-- They didn't disappear for me at anytime I've done a reset in the past, but I can't guarantee that.
As for contacts, use your 'people' contacts option/icon and hit the phones menu button-- you'll see an inport/export option. Use that and export your contacts to the SD card. You'll be able to import them the same way after the reset.
There's a work around for retrieving the apps off the sd card, as you won't be able to access the marketplace to redownload any apps.
Setup the phone to allow non market place app installations. I don't know about other backup programs, but I was able to search on the internet for 'astro download' and found several sites where I could download the astro app file directly to the phone. Make sure it's a reputable site though. I just installed astro after the download and was able to re-install my apps from the sd card.
If anyone has a problem with any of this, just ask. Hopefully my instructions aren't confusing.