HELP... Something similar seems to be happening to me. All of sudden around lunch today, my phone locked up. I did a soft reset. Now, my symptoms are as follows:
Phone boots, seems sluggish to come to start screen. After I reach start screen, power button will not work and phone eventually dims with even settings not able to change display brightness. However, control of the OS is still present and screen responds to all touch interaction. Eventually, the screen goes black and once it does, the phone will NOT turn back on without soft reset, and the cycle repeats. It is really bad. I was going to do a hard reset, but have been unsuccesful in getting a 100% backup to run. Seems to be hanging or failing around 98%. Any insight or assitance is appreciated. Oh, one other thing, soft reset always seem to work with Volume down and power, so it seems the hardware buttons are funtioning correctly.