If complaints by iPhone 4S users of poor battery life and audio bugs were not enough, TUAW reports that some of them are facing a peculiar problem where their iPhone 4S stops recognizing their SIM cards.

Based on this discussion thread on Apple support forums, users are reporting that they receive an error message on their iPhone 4S stating that they either have no SIM card installed or their SIM is invalid.

TUAW reports:

This issue doesn’t appear to be isolated to any one carrier or model of iPhone 4S, and it’s been happening to quite a few users since the handset launched. So far, the only sure-fire solution to the issue seems to be getting a replacement SIM from your carrier and swapping out the old one.

It’s not clear if this is a hardware issue specific to the iPhone 4S, a software bug in iOS, a bad batch of SIMs across multiple carriers, or some unlikely combination of the three.

Here’re some of the solutions that seem to have worked for some users after scanning through the discussion thread:

• Rebooting the iPhone
• Ejecting and re-inserting the SIM
• If iPhone 4S is hotter than usual, turn it off and let it cool down
• Get a new replacement micro SIM from your carrier (you can also try this if you are getting the error frequently)

If none of these solutions work or it is happening to frequently, it may be a good idea to visit an Apple Store and get it checked.

Have you faced any SIM card issues with your iPhone 4S? Let us know if any of the above solutions helped or if you have figured out another way to resolve the issue.

[via TUAW]