I had my Iphone 3G upgraded to 4.2.1 and jailbroke and hactivated with snowbreeze. I had problem unlocking it as installing ultrasnow using wifi on the phone failed. I couldnt connect to wifi despite having strong signal.
This one worked for me.
*NOTE; Originally answered by perfectpete216 and Edited by britta.*
Download links provided in the Original Answer! Just go to the "Unlock" category of most frequent asked questions and scroll down!!
You have to install ultrasn0w using iExplorer or DiskAid.
NB. you will need Itune v10 or later and Quicktime installed and run atleast once to use iExplorer.
Put the ultrasn0w.deb in var/root/Media/Cydia/AutoInstall
If the Cydia/AutoInstall directory is not there, then you create one by rightclicking/add directory then rename it to autoinstall.
Lastly, reboot your device.
Note: ultrasn0w has a dependency on Mobile Substrate, so if this is not installed on your device (if this is a fresh jailbreak it will not) then you need to download Mobile Substrate and Substrate Safe Mode and install them the same way explained for ultrasn0w. This should be done before installing ultrasn0w itself.
answered 03 Apr '12, 13:12