Do I have jailbreak my iPhone 3GS again after updating to iOS 5.1.1
If you updated with the official Apple update through iTunes, you're going to have to jailbreak again.
If you updated it using redsn0w or another program, you would still be jailbroken.
If Absinthe is hanging, make sure you have the latest version. There have been two updates as of the time of this answer.