Many "Code 5" style errors are caused by missing or incorrect encoding specifications, especially for books with Spanish characters (ñ, accents). : Use the Modify EPUB plugin in Calibre. Fix : Check the box for Encode HTML in UTF-8 .
You can find community-maintained fix packs on: lectuepublibre 5 fix
Improvements
You double-click the icon, nothing happens, or a window flashes and disappears. Many "Code 5" style errors are caused by