HT5192: About the security content of iOS 5.1 Software UpdateLearn about About the security content of iOS 5.1 Software Update
Currently Being ModeratedMay 21, 2012 1:54 PM (in response to Saukoreri)
You can try to plug it into iTunes and try to do the update that way. The download might of became corrupted or it can't verify the integrity of the update. You could also try to hard reset it by pressing both the home and power button for about 10 seconds. If all else fails, wipe the iPad back to factory defaults and try the update again. Not ideal but sometimes its the only way out.
Currently Being ModeratedMay 21, 2012 2:44 PM (in response to Saukoreri)
If you get a message that the update cannot be installed then it will never be installed. Start iTunes on your computer, connect your iPad and install the update that way.