This caused several problems. 1) Unable to install IOS 6.1.3 upgrade 2) The 4G functionality didn't work 3) The iPad would randomly reboot
My solution was to install a clean IOS 6.1.3 from scratch. Make sure you have a good backup, reinstall IOS 6.1.3 from iTunes and then restore the backup. After I performed these steps, the random rebooting stopped and my 4G service worked.