I updated my iPad 3 last night to 5.1.1 via a PC connection. All seemed ok and the aps were working. Closed the cover and the device died. Would not switch on again from the cover opening or the main on/off switch. I have managed to get it back on by using the hard reset (Home and Main switches pressed for more than 10 seconds). Seems to be ok now but is this behaviour normal? iPad 3 32Gb LTE model.