Has happened two days back to back - set iPhone alarms, use the top lock button to turn off screen. Wake up the next day to find the alarms haven't gone off, the home button not working and the white Apple symbol on black background showing indicating the phone crashed. Goes back to locked screen in a few seconds after that. Anyone else having his problem? Can't trust my phone as an alarm at the moment - already very nearly missed a job interview and an important meeting!