First, I have a Kindle2, jailbroken, font hacked, etc. I figured I would try this Palatino, because I like the font. And there should be no difference in changing fonts from K3 to K2, right? I've done it before, and have been using a nice Georgia2 font.
So, I added the Palatino font (of course backing up my fonts folder), and it looked fine -- actually, a little too fine for my old eyes, so I decided to try the Georgia. I copied the font to my fonts folder, but when I went to do a restart, I could not! I kept getting a pop-up window asking if I really wanted to de-register my Kindle.
Finally, I replaced my font folder with the backup and did a hard restart, and everything is back as it should be.
I think this may have been due to a spacing change in the font (I noticed that there was much bigger line spacing with the Palatino), which maybe caused some kind of mis-location of the cursor?? I haven't a clue. Anyway, my old Georgia 2 font is just fine. It is just that it is hard to resist funking around.