I've downgraded/unbricked a few PSPs through Pandora (Specifically, the setup described in the Perfect Pandora thread stickied) with no problems, both slims and fats, but I'm unable to downgrade a friend's PSP fat from official 3.51 to... well, anything.
The PSP works just fine, never run a cfw before, but once preparing the magic memory stick and the jigkick battery ala the Perfect Pandora thread, I can't get into the pandora menu at startup. I... hold down the left trigger and nothing happens. At all.
The most bizzare part is that the same battery and stick works just fine on my own fat, so I've no idea what I've forgotten to do, or whatnot. Any suggestions?