I have a normally activated iPhone that I upgraded to 1.1.1 the day it was available. I've been using my iPhone with a DIFFERENT AT&T account SIM card (Cingular), although I still have my real iPhone account. It has worked flawlessly since I started using it before the 1.1.1 upgrade. It continued to work flawlessly after the upgrade until this Friday afternoon (10-5-07). I was checking my email on the iPhone and suddenly it crashed out of email and said "please activate with itunes". So, I rebooted the iphone to see what would happen and it has now officially locked me out of using my other SIM. When I put the original SIM back in, the phone works fine, but as soon as I put my other Cingular SIM in it says: "Different SIM detected, please connect to iTunes". I tried restoring with no luck. Anyone else have a similar "sudden" problem using other AT&T SIMs that used to work just fine? Any suggestions for a resolution?...I would like to continue to use my other SIM in the iPhone.