doing a hard reset (holding the "power" button and the home button simultaneously) can seriously screw up OS files on your iPhone to the point where it will not restart properly so do it only as a last resort. my story has a happy ending but i thought i'd relay that little bit of caution. i was synching with iTunes and iTunes said that it was okay to disconnect. I disconnected the phone and it froze ... unresponsive to any input. tried a few other things but then decided to do the hard reset (power/sleep button and home button) and when i restarted the phone i got a bunch of text and a command prompt ... like you are in unix or something. what happened was doing the hard reset probably ended up corrupting a file that made it impossible to reboot the phone as usual. i thought it was a gonner but i took it to my local apple store and they did a complete clean install of the firmware and it is back to normal now - sans things that weren't backed up onto my home computer. i was very impressed with the guys at my genius bar. soooooo first try holding the "sleep/power" button for a few seconds until the shut off slider for power off shows up ... only do the hard reset as a very last resort. i'm sure this is obvious to many but i thought i would warn those who might not realize this. best regards.