I had my 3GS replaced at a genius bar a couple of weeks ago and I have been having problems with the new unit. Occasionally and randomly the screen will become unresponsive (this could be whilst using an app, or writing an SMS, or even just when using the home screen). When the unit does not respond pressing the Home button will return to the springboard however the touchscreen will remain un-responsive until I press the Lock button and then unlock the phone again. Has anyone had this problem or anything similar. I dont think it is caused by apps crashing because the app will still be doing whatever it was doing, the screen is just unresponsive. I have tried restores and no luck. Any help would be appreciated.