Hard boot or re-boot
Shut off and put on charger.
The pad would not turn on the next day.
A call to tech service had me hold the power and screen button for about 20 seconds, and the apple came up and the unit booted just fine.
Saved a long drive to the Apple store.
Hope this helps someone find a answer in search.
Here's how to troubleshoot
Help! My iPad wont quit app
Press and hold home button for 6 seconds or longer
1 If that doesn't work
Try switching apps (if you got the latest firmware)
2 If that doesn't work
Hold sleep button till it displays a "slide to power off" and turn it off
3 if that doesn't work
Hold home and power for 10 seconds
Help! The iPad won't turn on/ go past Apple logo etc
1 is it out of power then charge it
2 try synching it with iTunes
4 hold power button and home for 10 seconds
5 put it in restore mode (I said restore mode so if you haven't backed up your iPad you'll lose some data) by holding the home button till it displays a USB cable and a iTunes logo while plugged in to PC/Mac/Linux (with iTunes of course)
6 put it DFU mode (this is last priority) hold the power button and the home button for 10 seconds then release only the power button, now keep holding the home button for another 10 seconds. The screen should be black but lit up. the iPad should be plugged in a PC/Mac/Linux (with iTunes of course)