http://support.apple.com/kb/TS3281
Symptoms
Your iPhone, iPad, or iPod touch may occasionally stop responding to buttons, switches, or touchscreen input and may exhibit one or more of these symptoms:
- Does not return to the Home screen after you press the Home button
- Does not wake from sleep after you press the Sleep/Wake button
- Does not turn on (or power on) when you press any button
- Does not start up past Apple logo
- Appears frozen or unresponsive
- Is unable to “Slide to Unlock” or “Slide to Power Off”
Resolution
- If a single application is not responding or stops responding when it opens, you can force it to close.
- If the device is unresponsive or if certain controls aren’t working as expected, restart your device.
- If the device remains unresponsive or does not turn on (or power on), reset your device.
- If there is no video or if the screen remains black, verify that the device has enough charge to turn on:
- Ensure that the iPad is connected to the USB Power Adapter supplied with the device.
- Let charge for at least twenty minutes, then see if it starts normally.
- If there is no image on the screen, press the Sleep/Wake button to attempt to wake the device.
- If the screen displays a red battery icon, continue charging the device until the battery is fully charged.
Troubleshooting touchscreen response
http://support.apple.com/kb/ts1827
Symptoms
Use this article to troubleshoot the following Multi-Touch display (or touchscreen) response issues:
- Multi-Touch display (or touchscreen) does not respond
- Portions of the Multi-Touch display do not respond
- Multi-Touch display is very slow to respond
- Multi-Touch response is erratic
Resolution
If your device is experiencing any of the symptoms listed above, try the following steps:
- Restart your device
- Hold the On/Off button until “slide to power off” appears. Slide to power off your device. When it is off, press the On/Off button to turn it back on.
- If you can’t restart your device, reset it by pressing and holding the Sleep/Wake button and the Home button at the same time for a least ten seconds, until the Apple logo appears.
- Clean the screen with a soft, slightly damp, lint-free cloth.
- Avoid using the device while wearing gloves, with wet hands, or immediately after applying hand lotion.
- If you have a protective case, or if you are using a plastic sheet or film on the display, try removing them and testing the device without it.
Additional Information
Tip: To isolate an issue related to a portion of the Multi-Touch display, follow these steps:
- Open the Maps application and double-tap each corner, then the center, to verify that it zooms in to each section.
- If a specific area is affected in another application, note the location and try to verify touch functionality for that location in the Maps application.