Do you have a systems folder? Is there a common pac file in there? If there is, is it named common#.pac or common#_en.pac?
Whatever it is make sure its consistent with the selcharacter pac you will download from the resources tab. What I mean by consistent is that if it ends in en for your common#pac may sure it ends in en for the sel character pac you will download.
Resources
http://forums.kc-mm.com/Gallery/Resources.phpScroll to the bottom and clock the down arrow for the data partition you're using. Region PAL or Region NTSC. It's labeled.
Go into the menu2 folder and find a sel character pac. download it.
Open it with brawl box.
Make your changes. Save. Copy it to your sd card
X://private/wii/app/rsb*/pf/menu2
Then Use brawl box to open your common5 pac located in the systems folder
X://private/wii/app/rrsb*/pf/system
(It should be there..)
Replace the selcharacter_en.pac with the one we just saved. Make sure its renamed to "selcharacter_en.pac" because thats what brawlbox is looking to replace.
Save.
Try that.