You didn't change the size dimensions of the names, did you? The size dimensions of your names MUST match that of what you're replacing.
For example, Mario's CSP name is 144 pixels wide and 24 pixels tall. If you're replacing that name, the new name has to use the exact same size dimensions.
Also, the CSP names use the I4 texture format, so you're making a huge mistake if you change the texture formats.
like mnsg said, leave all your custom files exacally like what the original had, and make sure you back up the originals before you replace.
I also found that...even though your file is below the size limit.....it still can cause problems, just go over that file and fix it up
I compared both files and they had the exact same dimensions, format, everything.
I was replacing Marth with Sephiroth. Both were 144x24 and I4 format.
My Naruto over Ike one didn't match up in terms of dimensions; Naruto was bigger than the Ike tag. But my Sephiroth one should have worked.