I just want to let you knoe about an experience I had with the psp font hack program. If you run it so that you change the fonts on your psp's main screen then it will rely on your memory card to load these fonts.
I had the brilliant idea of loading up my psp without my memory stick in and no letter or numbers appeared when it went to the 4 digit passowrd thing I put on so it won't auto load the umd.
I hit o as I usially would and was going to restart it with the ms in, but when I hit o I got the blue screen one would get whilst downgrading and it had to restore system info.
This in no way hints to a possible downgrader, I just wanted to let people who use the font hack to know that they should install a font on each of their memory sticks so they don't have their psp fully reset.