My sister jailbroke her 4s (I'm staying pure), everything went fine, she restored her apps, turned her phone off, the Cydia app was on her homescreen, everything was looking good. But when she clicked on it nothing happened! the screen goes black for a minute and then goes back to the homescreen. We tried restoring, applying Absinthe again but the the programs gives a message saying the device is already jailbroken.
We've been searching google for a solution but so far no luck.
Had the same problem for some reason after I installed winterboard. Thought about doing a restore but didnt really wanna take the time so I just rebooted the device and it works fine but I dont have a 4S so hopefully its not to different.
I would restore using the 5.1.1 Ipsw and use shirt restore then re JB them load Cydia etc before restoring info from a backup if after your restore info Cydia crashs again then you know it's your back up causing the issue