When i signed up for at&t in january, i got a SE w580i, because it was free. the SIM in that thing was active for about 2 hours, because i activated my iphone. so the w580i's sim was no longer active. Now, last week i gave the iphone to my girlfriend, and i figured, ok i will put the at&t sim thats not active in the iphone, and it will activate thru itunes, and switch her number to the new sim. that didnt happen. i ended up having to use her cingular sim card in the iphone. itunes activated it just fine. Only thing is, apparently its freezing on her. i know there were a few bizarre moments the first day i activated it, like at on point, all of her contacts disappeared, and then reappeared after a restart. then, her data was not functioning whatsoever, which was also fixed with a restart. Do you guys think that the cause of all these problems is because she has a cingular sim card? everything is legit, i've never jailbroken or unlocked it at all. i used the iphone for about 2 months, and never had even 1 problem with it. any ideas are very welcome!