I'm not sure what's wrong. When I imported them, it created the folders correctly and added all the materials from the "C:\Program Files (x86)\MangaStudio EX 4E\Settings" folder.
Your error message says, "Failed to convert materials and templates" so maybe your materials are corrupted..? Perhaps you could re-install the MangaStudio Computones CD library and try import them again?
And yea.. the current material install system is crap.
If you actually install all of these tones btw, your CSP will take about and extra minute to load, it's so slow
Edit:
From the materials you manage to import, are they creating keywords at all? e.g.
