So I am having an issue with Yellowsn0w. When I install yellowsn0w my AT&T sim card won't work. When I try to make a call my signal craps out. This also happens with incoming calls as well as text and data. Once I uninstall Yellowsn0w everything goes back to normal. I'm not sure what I am doing wrong. Also, my T-mobile US sim card (Pay as you go) doesn't work as well. It always shows as an 'invalid sim.' But, I think that is happening to everyone. Thanks for the help, Aaron. oh, I am using a 16GB black 3g iphone.