As we reported a few days ago, Apple has released a new build of iOS 5.0.1 specifically for iPhone 4S owners — but now we have official word from Apple as to what this update brings. Officially, this new build is designed to fix the pesky "No SIM card" errors that some users have experienced, though there's also new access to the iPhone's file system, which may enable loads of Siri hacking. Unfortunately, this isn't a delta update (which allows you to download only the updated parts of the OS over the air) — you'll need to back up your iPhone, download the software update, and do a full restore from scratch. Still, that's a small price to pay if your phone's SIM card has been acting up.