If you hit a black screen it can be many things, by the way you know you must edit the sfo too ? Ever thought about upgrading to REX or Rogero ? My fix you problem and no more patching , downgrading can be don via the 9999 downgrader if you wish there is no reason staying on 3.55 anymore.
PS: I heard some lego games are problematic regardless the CFW
So your CFW seems to be badly outdated. You should really get a new CFW. To be on the save side first apply QA flag pls (You can find the QA flag pkg's on ps3news), pls check if you QA Flag worked !! Before doing anything !
Than go to Rescue menu, by keeping your finger on the PS's power button till it beeps 3 times and install you CFW of choice from USB stick , I'd recommend to pick a updated one like REX or so.
PS: Why do you still use a dongle they are outdated as hell ?