I have and Ipad2 and heres what has worked for me so far. Settings, Reset all settings, turn on wifi, App store, update all, allow time to update all, yes this blows.
Hope this works for you. Very disipointed Apple should have caught this bug.
iPad mini has this issue, iPhone 4S does not. Have been able to update using the purchased tab. Very annoying as some of the apps under under my apple id and some are under my wife's so I have to login in/out to update. Nice that I didn't have to pay for the apps twice but annoying when issues like this arise.
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All we can do is be patient until things get sorted out with the Apple servers. Some are effected while some of us are not.