iPhone 4S SIM cards failing, even on CDMA networks

No, that's not a typo. Customers are reporting SIM card failures across all carriers, including CDMA-based Verizon and Sprint, which actually use the micro SIMs included in the iPhone 4S to roam on GSM networks as part of the "world phone" experience touted by Apple.

AT&T customer and Apple Support Communities member "robsdoghouse" experienced SIM card failure just after purchasing the iPhone 4S.

"I started experimenting with Siri and a couple minutes later the phone was hotter than usual and I get Sim Card failure, and Bad SIM messages."

Over 17 pages later, many users are still baffled by the mysterious SIM card failure messages. SIM card failures aren't quite uncommon with GSM networks like AT&T that use the card to authenticate their users' accounts and grant service access. The fact that this failure is occurring with CDMA iPhone 4S models is, however, odd. ASC member "jpd60" reports that the issue is happening on his brand-new Verizon iPhone 4S:

"I cannot activate the phone if the SIM card is in the slot regardless of the fact that the Verizon network does not make use of it. If I remove the SIM card, I can activate the phone and everything works fine but as soon as I put it back in, I get a message that the phone has to be activated (which I can't do)."

Several suggestions for solving the issue have been presented, though it seems like the best one may be to simply restart your iPhone 4S. While restarting does seem to alleviate the problem initially, many users still report the SIM card failure error messages returning.

One user, "Salo0ol," thinks the issue could be tied to the Cellular Data setting (Settings > General > Network). After setting this to "Off" the SIM card errors did not return. Upon turning it on, they did.

With Apple already reportedly working on an iOS 5.0.2 update to readdress battery issues, it would make sense that it would address this SIM failure issue as well (assuming the problem is a software one), though no mention has been made of it directly from Apple.

Until then, if you are experiencing SIM card failure problems and restarting your iPhone does not alleviate the issue, try restoring it completely in iTunes. If that does not work, make an appointment at your closest Apple Store Genius Bar or third-party Apple service provider to get the phone checked out. Many users are reporting that they were able to secure replacement phones when doing so.

Have you experienced SIM card failure issues on your iPhone 4S? Let me know in the comments!