MP Cost - The Lost 3rd digit

Trying this out. Not only does the little window not display anything, but trying to view the Magic menu crashes the game.

You got another entry here (and its pointer at C3/4D00). It's for the main skill menu. What you've changed is for the sub-skill menu.

Code:

C3/5C63:    0D7B 81A5A2ADB300              ; Blitz

Your screenshot seems fine. One problem could be 8 letters is not legit for a reason. Otherwise you'll need to do some tracing in C3/02F9 to see if it is executed properly.