Originally Posted by Kobudera
I did anything as you asked. I installed suitable Jailbreak and Font Hack too. My Kindle's fw is 5.1.2.
However Kindle still ask me the Jailbreak. What will I do? Please help me! Thanks a lot.
Well, you obviously didn't do everything that is required. Did you read the README? Did you follow the instructions? If not, did you wonder why the file is called README?
...I bet that it's complaining about the Kindlet Jailbreak. So... guess what: install the Kindlet Jailbreak