I've had an unlocked 2g and 3g thanks to the dev team. However last month i decided to switch to an O2 simplicity plan, thinking that using an O2 sim will mean i will not have to worry about unlocking and updating basebands etc (i.e. i'll be able to install 3.0 on the 17th and not have to wait for the dev team). When I got my sim I did not bother to restore the phone or uninstall yellowsnow. A week ago i attempted a restore (I still used a custom firmware incase i was wrong so I'm still on 2.28) without yellowsnow. However I could not get any signal at all, so i reinstalled yellowsnow and was able to get signal fine. Anyone have any ideas as to what's happening? Is it possible to use any O2 sim card in an iPhone? Is it not working because I need the updated baseband? Any insight into this would be very much appreciated as i'd like to be using 3.0 the day it comes out. Thanks all!