Apple iPhone Troubleshooting Assistant
(following is from the Apple Troubleshooting Assistant Web Page - click link above to go there)
Restart 
Try restarting iPhone. To turn it off, press and hold the Sleep/Wake button until the red slider appears. Slide your finger across the slider to turn off iPhone. To turn iPhone on, press and hold the Sleep/Wake button until the Apple logo appears.
Reset  To reset iPhone, press and hold the Sleep/Wake button and the Home button at the same time until you see the Apple logo.
Does iPhone appear frozen or stuck? Try pressing and holding the Home button for 6 seconds to close a frozen application. Then try restarting iPhone again. Reset  To reset iPhone, press and hold the Sleep/Wake button and the Home button at the same time until you see the Apple logo. | 
