I would suggest if you are looking to jailbreak a 3GS or iPhone 4 running 5.1.1. Use Redsnow to apply a tethered jailbreak, then once Cydia is installed. Search for the 'Rocky Raccoon' un-tether package. Install it and then you will be un tethered.
I suggest this as Absinthe seems to be hit and miss with a4 devices.
I suggest this as Absinthe seems to be hit and miss with a4 devices.