A view days ago we told you guys about a new build of iOS 5.0.1, that Apple released without any notification. We did not know why Apple pushed a new update to the iPhone 4S, but now we know. It turns out that this update fixes the “No SIM Card” errors that some iPhone 4S users have been experiencing.

Based on a new Apple support document, it now appears that the updated build may have been designed to address an issue some users have been experiencing with SIM card-related errors. With the update affecting a relatively small portion of users, Apple may have elected not to push it out to all users in the form of an iOS 5.0.2 software update, and instead rely on those users who are having problems following Apple’s advice and obtaining the new build through the restore process outlined as a solution for the issue.

In certain situations, iPhone 4S may have difficulty recognizing a micro-SIM card, resulting in the following behaviors:  “Invalid SIM” or “No SIM Card installed” alert appears intermittently. Status bar displays “No Service” or “Searching” in a location with good network coverage. These Problems should now be resolved.

Unfortunately, user reports on the new build appear to be mixed, with some users reporting that it does indeed fix their “no SIM card” issues while others have seen no improvement.

Source [macrumors]