Anyone having this problem, would be in a conversation, and the handheld will just rest itself? What causes it, and how can it be resolved? I must add, its an unlocked 7100g, with tmobile now.

Same problem with my 7100g. No pattern to it. I personally know of 2 others that have the same problems. All 3 phones are with SunCom. I've met 2 other users with Verizon having the same problem.

What OS are you guys running? My 7130e does the same thing sometimes. It might be the OS or some 3rd party software that's causing the resets. The only 3rd party software I have right now is Ramble IM and I only use it when I'm at work.

Is this what you mean?

v4.0.0.219 (Platform 18.0.129)

no addtional software other than what came on the phone.

You might want to call warranty exchange and have your device replaced if you or whoever you purchased it from got it from the wireless company and not eBay or see if RIM can assist you.