Apple surprised us by quietly releasing a tweaked version of iOS 5.0.1 for iPhone 4S users. Though the build number (build number of original iOS 5.0.1 was 9A405) suggested that Apple may have fixed some minor bugs, the details were not available.

MacRumors has just reported that according to a new support document, Apple has fixed the annoying SIM card issues that has plagued iPhone 4S users.

Some iPhone 4S users have reported that they receive an error message stating “No SIM Card installed” or “Invalid SIM” on their shiny new iPhone.

MacRumors reports:

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.  

The new Apple support document provides details about 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.

The support document goes on to explain how iPhone 4S users facing the SIM card issues can fix the problem:

1. Back up your user content and settings using iTunes or iCloud. See this article for more information.
2. Restore your iPhone 4S using iTunes.
3. After the process is complete, restore your user content and settings from your backup.
4. To confirm that you’ve successfully restored, verify that the version is now iOS 5.0.1 (9A406) in Settings > General > About.

MacRumors reports that some users have reported that the tweaked version of iOS 5.0.1 fixes the SIM card issues, while others have reported that they’re still facing the problem.

If you’re facing the problem, let us know how it goes.