I'm at the end of my rope, and totally out of ideas of how to fix this problem, so I'm taking it to the forum. I'm really hoping someone can help me out. I did a search and found a similar thread, but I tried all the fixes listed there, and the OP didn't post what ended up working for them. So here goes.
I have 2 ATT Pre3's. I'm actually having the same problem on both, which makes me believe that I'm doing something wrong or that there is a fix that I'm missing. I also just set up my ATT service. My SIM card works on my HTC Surround, and everything works fine (except that it doesn't have webOS).
When I tried to fire up the first Pre3, I was in an area with really crappy reception. The Pre3 was trying to restore my profile, but was painfully slow. I just randomly did a back gesture, and it freaked out. Once it came to, it kept rebooting itself. It does the initial HP pulsating logo, then transitions to the ATT 'Rethink Possible' screen briefly before flipping back to the initial HP logo. Randomly, it'll boot all the way, but if I touch the screen, it stutters and goes back into the reboot cycle.
I first tried soft and then hard resets, and battery pulls and it wouldn't break the reboot cycle. I then took it to the doctor (which was a royal pain since it was constantly rebooting). I was able to run the doctor once, but once I got through the profile restore, it just goes into the same thing. I've also let the battery run down then recharged, but it just immediately going into the reboot cycle.
The crazy part was when I cracked open the second Pre3, the same thing was happening. I really have no idea what I could be doing that would cause this to happen.
Pre3 is constantly rebooting on the 'Rethinking Possible' screen
Battery pulls and doctoring does NOT change the behavior
Happened on 2 different Pre3s (both are ATT versions)