I have an iPad 3 (16GB, no 3G), running iOS 6. Three times recently it's got into a state where when I've turned it on (from sleep, not from completely off), and I haven't been able to enter my password. I can 'slide to unlock', but when the keyboard comes up, the cursor flickers, but all the 'keypresses' don't do anything (although, for example, the 123 key on the keyboard still works). I've also noticed that the orientation sensor doesn't work when I rotate it in this state (the lock switch is off).
Has anyone else seen this issue? Is it a known problem? How can I fix it? So far I've fixed it by turned the iPad completely off and on, but obviously that's far from ideal.