I am having the same problems.. I have a jail broken unlocked iphone working on T-mobile. I upgraded to the official release of 2.0. I downgraded to 1.1.4. Here's the problem i couldn't make calls. Like everyone else my modem was 4.5.4. So i stumbled onto this site and tried with no success all the steps over and over and over. Every time all went fine but the modem wouldnt go back to 4.4.5. So i thought maybe the problem was that i was still using my t-mobile sim card. I went to lok for the at&t sim and couldnt find it. lol i guess i tossed it. So i bought a new sim and today have tried all this over again. Still no luck.... has anyone else been stumped and then finally got it?? ill take any suggestions. I havent had a phone since friday and my life is in that phone. I do have a restore point so all my info is safely waiting to be put back into the phone??? please help????