if you don’t have the original SIM for activating you may have problems as described.
i did it, having an unlocked iPhone 4S using SAM like this
1) download the firmware for my iPhone 4S 5.1.1 : iPhone4,1_5.1.1_9B206_Restore.ipsw
2) install the last iTunes 10.6.1.7
3) connect the iPhone on the original cable to iTunes and do a Shift + RESTORE and choose the downloaded iPhone4,1_5.1.1_9B206_Restore.ipsw .
4) it will require to activate, i did used my gevey ultra sim with my network operator sim which worked well on 5.0.1 and activated the phone on 5.1.1 .
5) download the absinthe-win-2.0.1.zip and unzip the exe, run it and it will unzip in a folder, run as Admnistrator absinthe.exe , it will see the device, and press jailbreak, install in cydia then openssh.
6) you can remove the gevey sim card and put the original sim tray with you network sim card for who you have the SAM backup, it will require you again to activate, you must download i-FunBox navigate to raw file system to /var/root/Library and delete the Lockdown and copy the old one used for SAM , and do a restart to the phone and wait, it will see it as a new iPhone and pass activation and have also signal.
they did it 😀 it’s out the jailbreak for the 5.1.1 firmware, you may wanna take a look if you have an iPhone here .