Phone/Configuration: Atrix 4G, pretty much the way it came from AT&T (added a few apps from Google Play, adjusted settings, etc.). Symptoms: Random reboots regardless of how it was (or wasn't) being used, EXCEPT in Airplane mode, in which case it wouldn't reboot. Timeframe: I noticed it happening a few times when I first purchased the phone in July 2011, but chalked it up to having purchased "bleeding edge" technology. Somewhere around April 1, 2012 it started rebooting approximately once per hour. AT&T sent me a replacement phone this week. It rebooted while I was setting it up. It also rebooted at least once per hour. I used the "Reboot Logger" app to track the reboots. Thanks to the following threads for helping me narrow it down (since I'm not a frequent poster I can't post links, so do a search for the following): "Atrix Random Reboot Issue Poll" "3 different ATRIX phones all rebooting" I did quite a bit of searching on this topic, both when I first got the phone and recently when it got bad. I didn't find the last thread above until yesterday. I had AT&T replace the SIM card yesterday evening and it seems to be working fine now. If this is common, it's difficult to believe it doesn't seem to be more well known by either the carriers or Motorola. Maybe the Atrix is just more sensitive to bad/sketchy SIM cards? I'll try to remember to edit this post with updates, but at this point it seems to be case closed. Hope it helps some frustrated users. 12 hrs with no reboots. 24 hrs with no reboots. 48 hrs with no reboots. 1 week with no reboots (this will be the last update unless problems start again).