If you are on a 3G iPad and check your “Cellular Data” and click “View Account” and get a USIM9997 error, it could be a simple fix.  I was connected to the internet via WiFi since it is fast.  Apparently if you are not connected via the AT&T network, you will get an error.  So, it turns out that turning on “Cellular Data” so that you are using the AT&T 3G network fixed the problem for me.  Just a helpful hint.  😉