You can't downgrade a PS3 OS without bricking it.
Req close
/moved .
you cant downgrade 3.60
upgrade to 3.62 and jailbreak.
Lol, you've got a major problem. Unless you have the 3.55 patch on a folder in your computer or on a usb, your fucked. USB is the only way to downgrade without bricking your system. Even if you manage to find a 3.55 and downgrade, might as well turn auto updating and everything off.
Would be really hard, I wish I can help you, but i don't know anything about JB'ing PS3
Sorry mate you can't do it, there is 1 way but it's real expensive!