Hello ...last night my 3G data just stopped working all of a sudden. Had been working fine all night then nothing...didn't even show a data ip in sbsettings. Also, in settings, the view account tab had disappeared under cellular data. And, in the About tab, the carrier entry said Not Availible. When I plugged it into my pc and started iTunes, it gave an error message that said " Couldn't check for update to carrier settings" 1631. AT&T put a new sim in and that didn't fix it, I just got done doing a restore in anticipation of a visit to the Apple Store and that fixed it. Has anyone else had this problem? I didn't install anything last night that should affect it, like I said...it had been working fine all night. Hoping to get a bit of insight before I put everything back on it.