This is a bit drastic, buy you could try Reset All Settings under Settings > General > Reset. It won't delete any of your content, apps, or accounts, but it will default most of your other settings, so you will have to go back and re-tweak things the way you want them. If that does not work you may have to restore the iPad using iTunes and a computer. That's been the final fix for some of the more persistent problems people have had after the update. The OTA update isn't as reliable, since it does not overwrite the existing OS, but patches it. The iTunes update is a clean install of the OS, and less likely to encounter problems. The bug that's been going around and that Apple is supposed to fix has to do with undelivered messages, so it's unlikely that it is related to your problem.