I renamed one of my songs "What a Wonderful World[F] - U3A" and typed in "World" in the search text with it set to "All Fields", and the song is still shown in the list, as I would expect. I'm going to need to know what other settings you may have changed under Settings->Library Settings such as unchecking "Normalize Characters". Also, please verify that you haven't entered a different value for "Sort Title" for that song.
Thanks,
Mike
Thanks,
Mike