I'm dealing with a bug that's been reported on and off since about mid-December (the last update). The overheat/battery drain is due to the native SMS. At times once a SMS is received or sent, the system runs away on processing and the phone will be dead within about 40 minutes, or shut off due to overheat. The only fix is to reboot once it starts, or go into Airplane mode for 5 minutes so the stuck process terminates. Not sure what the fix will be, as HTC doesn't seem to be acknowledging it yet. Even after deleting all the SMS's on my phone it overheats immediately when I get or send an SMS at this point, so I have to reboot it after every q360 page ect. Some people have gotten RMA's for HTC and it does the same thing immediately out of the box. Hope there's a fix soon.