I've been having this issue since the first few days I've had the moment, which was about three weeks ago. I've never noticed airplane mode being turned on, but it seems like once every couple of days, my data connection will crap out (as in, Pandora hangs, google maps stops updating, etc), then after a few seconds the signal drops to nothing and I get thr little x in the corner of the meter.
I use an app called Switch Pan, it provides quick shortcuts for data, 2g, wifi, BT, etc. When I see this glitch, BT and wifi both work just fine, but Switch Pan shows the cellular radio is turned off, and no amounts of fiddling with that app or my phone options will allow it to turn back on. I've tried everything I can think of, turning off all the other radios, playing with roam settings, nothing short of rebooting the phone will get it to come back.
As soon as I reboot by holding down the end button, selecting power off, then booting back up, everything is fine. The radio comes back up to full signal, or whatever strength I normally have in that area, and I usually get a handful of alerts for new VMs and texts.
When I first got the phone, it seemed related to wifi. However, now I keep wifi turned off most of the time to conserve battery and I still see it. It's happened at home sitting at my dining room table where I get 1mbps download speeds, it's happened on the charger, on the road. I can't find any pattern to it. After getting frustrated of having to frequently reboot and wait for this beast to load up, I finally did a google search and came across this thread.
After seeing everyone else's experiences, I'll try uninstalling my toggle apps, paying attention to if I've used wifi recently, updating the profile, etc, and see if I start to notice any patterns.