This is truly bizarre. I have iPad 1 running 4.3.3 JB. I was able to sign in the App store to download apps until yesterday. However, since then, the App store keeps showing a "sign in" button instead of my account ID name, even though in settings I had already signed in. Tapping on the "sign in" button does NOTHING! Reboot the iPad (hard reboot) does not solve the problem. I can sign in and off normally from settings, but not the App store. I have not installed or tickle around the iPad otherwise. Can someone please help?