I am using I Pad 3G 64 GB, while installing the cellular card for the internet, the I Pad suddenly crashed.
I have tried to push the sleep & home buttons altogether for about 10 seconds until the Apple sign appear on the screen but nothing happen afterwards and the I Pad wasn't able to turn off.
I hope someone can help me to solve the problem.
Thank you for your kind help.
Was the iPad switched on when you tried to install the SIM card? (Not a good idea). I would remove the SIM card (if it's still in the iPad) and try to power up the iPad again (if it didn't switch off after you did the hard reset I guess the battery has gone 'flat' by now, so you might need to charge it up for a while).
If you can get your iPad powered up again, only install the SIM card with it switched off (forgive me if I misunderstood your original message). I have the same iPad as you and have not had any problems. Installing the SIM card, though, is not 100% intuitively obvious and I nearly tried to install mine the wrong way around (though, realistically, it should only fit one way round!).
Post some more details if you're still having problems - every little detail will help the Forum members understand your problem.
Don't worry, though! It's pretty difficult to permanently damage the iPad. Have faith in the technology!!
Tim
Scotland