I've had a similar problem. I updated to 5.1.1 and jail broke with absinthe from a jail broken 5.0.1. (iPhone 4S)
Issue I have is when I try to install SBSettings, cydia doesn't show any information on the app and when I tap confirm it either pops up with a HTTP error or a hash check error. Not sure if something went wrong with the jailbreak or if it's an issue with a source.