Random reboots are usually from one of 2 reasons...
1) an Application crashed or hung up the system... (think of how a Windows PC will "Blue Screen" or just reboot)
2) you have an application (or too many applications) that are eating up system memory to the point the phone just crashes.
Remember, smart phones are really just little, handheld PC's. An Android phone is nothing more than a Linux based computer you can put in your pocket and make phone calls with.
The "Blank Screen" where you have to pull the battery is nothing more than a worse case of the above. The phone locked up to the point it could not reboot itself. Again, just like when a PC locks up to the point you can't reboot it and you have to hard power it off.
Go in, look at what applications you have running. Launch the Task Manager app and see what's running in the background. Any that are not needed, long-press on them and add them to the Auto-Kill list.
Also, reboot the phone once in a while. I reboot mine every couple of days, regardless of if I think I need to or not.
So I have a similar problem:
1) Phone reboots randomly.
2) Calls drop in the middle even though the signal strength is fine.
3) Phone won't respond to touching the power key to get the home screen up. If I leave it in this mode for a couple hours, the battery starts to heat up heading toward a meltdown or fire.
4) Downloading apps from the Android market, the IP connection seems to hang or reports back failure, yet when I look, the app has been correctly installed on the phone.
Number 3 seems to happen especially often after using a data app like Google Maps or downloading from the Android Market, and when moving from one ATT coverage area to another.
I've seen other reports of this problem after an Android update (and for the Atrix 2 as well).
I've looked at my task list, there is nothing I'm running that seems especially suspicious (I don't download a lot of apps). I have no clue what the system apps are and am reluctant to just start killing them. Besides, I don't think that would fix the problem of calls getting killed in the middle of the call.
I really like the Atrix, especially the fingerprint recognition unlock, but I am now to the point where I am about to get another phone. What does Moto customer service say about this problem?
jak