Put your ps3 into recovery mode and click on update via storage media and update the OFW 3.55. To boot into recovery mode hold your finger on the power button on the ps3 it will beep once, then another time, and on the third beep take your finger off and it will shutdown. Then do the same thing until you hear it beep twice really fast, you are now in recovery mode.
After you have installed the CFW just go down to blackb0x and you should beable to highlight over it and then press triangle and then delete.
let me know if you have any more questions.