Well, Dantarion got mu_menumain.pac to work with that, so I assume it might be the texture itself. Test it by putting the original title screen file in there and see if the game treats it normally.
SD loader works with it. The path was posted in Dantarion's video a few weeks ago. It's something wierd, like pfmenu/whatever.
I posted a link to the video Dantarion posted, and the working path for ALL menu2 files was posted in the video description. Since wii can't copy/paste, head back over to the help section and look in that thread asking about the title screen and the SD loader. Mu_menumain works with it too.
And it should only freeze if you edited it incorrectly(erased those boxes between titles) or put really odd characters in there.
It's doesn't have anything to do with the song title being too long though. I've seen massive titles work with this(Three Minutes Clapping: The World Ends With You).
My friend made gave me an excel document for both music and textures. I refer to it whenever I want to switch something. For textures, I mostly refer to it for characters who don't have definite pallete swaps(Ice Climbers).