FuriousMod iOS5 Fix by mcbaron15 Unlock iPhone4 with Gevey Ultra on 5.0.1
It has come to our attention that the FuriousMod repo is not currently working and also the official FuriousMod package that is available does not work on iOS5. For those with an iPhone4 on 5.0.1 who have a compatible baseband(anything but 04.11.08) you can do a manual installation of the Furious Mod 5.0.1 deb from a MacRumors users, mcbaron15, which will allow you to use a Gevey Ultra on the latest iPhone firmware.
The easiest way to install the deb would be to use iFile. Simply transfer the deb file to any folder in your iPhone(make the location easy to remember). You can do this via SSH with Cyberduck(mac) or WinSCP(windows) or you can use a USB transfer program such as iFunBox. After you have transferred the file to your phone open up iFile and navigate to the folder. Select the .deb file and choose "Installer" when it asks you what to open it with.
Once you reboot your phone you will be able to use your Gevey Ultra SIM! If it doesn't work for you at first, try switching airplane mode on for a few seconds and then turning it off(thanks to Krisz for the tip!)