I made an attemp to jailbreak my iPad 2 5.1.1 recently using absinthe 2. During the jailbreaking process, there was some problem with the connection so the cydia though installed but not working. When I tried to do the jailbreak again, the program said this device is already jailbroken. I then use redSn0w but still no luck. Anyone here can help me?

Hi and welcome to the Forum!

I've moved your thread to our Hacking Section where you will receive a better response.

Do you have blobs for 5.1.1 saved? You can use this tutorial to find out - HOW TO - Save your SHSH Blobs with TinyUmbrella

If so, you can re-restore a clean fresh 5.1.1 on your device using this guide - TUTORIAL - Re-restore IOS 5.x on iPad2 and iPad3 using redsn0w and SHSH Blobs. After that, I advise that you jailbreak with redsn0w and not Absinthe.

If not, I"m not sure what to suggest. Sorry