same thing is happening to me, i just receive my card yesterday, and when i turn the phone on, it says Tm.... but with the five bars, and after two minutes it loses signal and then its says NO SIM. I have to turn off the iphone in order to make it work for another two minutes! in those two minutes i try to send messages and it didn't work. My iphone 3G is firmware 2.1, and is not jailbraked. If someone knows how to fix this plz tell us, im tired of freaking ATT
i bought my sim adaptor here
Unlock iPhone 3G Turbo Sim Card Any GSM No need to cut - eBay (item 280265749310 end time Sep-17-08 23:28:00 PDT)