If you used Greenpois0n Absinthe to untethered jailbreak iPhone 4S or iPad 2 then you might notice that the camera roll is empty. It only happened to some users only but you can find the solution from here.
PlanetBeing has tweeted that this is not the error but missing the full completion of jailbreaking. The solution is very simple. All you need to do is to rerun the application again to fix it.
You can follow our instruction here to untethered jailbreak iPhone 4S and iPad 2 running on iOS 5.0.1.