Rooting of Samsung Galaxy S2 didnt work - LPB kernel
I solved this by following the feedback from this phandroid post

I used the next higher kernel that is LPD and it worked! .LPH kernel as suggested by another answerer, did NOT work.

The original solution :


  Hi, I had the same problem which stumped me as well. I found the answer on a different thread; just use the kernel that is the 'next one up', which in this case is LPD. Works perfectly.


Adding it here just in case someone else comes looking.