Originally Posted by tsac
I would not jump to a new phone just yet. As you have seen in other posts, it may never happen again. I also have had this problem and simply cleaning the SIM cleared the problem. The SIM cards from ATT are no different than the ones branded Cingular unless it's an older 32k SIM. Then you need a new one at 64K
God help him if he is running a 32K card still...
Since you are not you are saved by the grace of God, lol.
I have also found some of the SIM cards to be more problematic depending on what company manufactures them. The cards manufactured by Gemplus with the more complex contact "design", I have seen fail more times in more phones. I couldn't tell you why, just what I have observed. I didn't intend for him to jump the gun and just replace the phone and if my post sounded like that was what I was telling him to do then my bad. I told him to try a few things before replacing the device, but if he keeps getting a SIM card error and it isn't the SIM or software, the phone is having some issues with hardware. If it stops happening then he doesn't have anything to worry about for the time being. Still, back up your stuff, you don't want to lose it!
Hopefully cleaning the card will do the trick for him, it is the easiest route.